Filed Pursuant to Rule 424(b)(3)
                                                    Registration No. 333-108789

                           PROSPECTUS SUPPLEMENT NO. 6
     (To Prospectus dated December 17, 2003, as supplemented by Prospectus
  Supplement No. 1 dated December 30, 2003, Prospectus Supplement No. 2 dated
     January 9, 2004, Prospectus Supplement No. 3 dated February 12, 2004,
        Prospectus Supplement No. 4 dated March 22, 2004 and Prospectus
                      Supplement No. 5 dated May 5, 2004)

     This prospectus  supplement  supplements the prospectus  dated December 17,
2003, as  supplemented  by prospectus  supplement No. 1 dated December 30, 2003,
prospectus  supplement No. 2 dated January 9, 2004,  prospectus supplement No. 3
dated  February 12, 2004,  prospectus  supplement No. 4 dated March 22, 2004 and
prospectus  supplement No. 5 dated May 5, 2004, of DoubleClick Inc.  relating to
the  resale  from time to time by  selling  securityholders  of our Zero  Coupon
Convertible  Subordinated Notes due 2023 held by certain securityholders and the
shares  of  our  common  stock  issuable  upon  conversion  of the  notes.  This
prospectus  supplement  should be read in conjunction  with the  prospectus,  as
supplemented, which is required to be delivered with this prospectus supplement.

     The  securities  offered  hereby  involve a high degree of risk. You should
carefully consider the "Risk Factors"  referenced on page 4 of the prospectus in
determining  whether to purchase the  DoubleClick  Inc. Zero Coupon  Convertible
Subordinated  Notes due 2023 or the common stock issuable upon conversion of the
notes.

                               -------------------

     Neither the  Securities and Exchange  Commission  nor any state  securities
commission has approved or  disapproved  of these  securities or passed upon the
adequacy or accuracy of this prospectus  supplement.  Any  representation to the
contrary is a criminal offense.

                              -------------------

     The seventh  paragraph of the section of the  prospectus  entitled "Plan of
Distribution"  on page 52 of the  prospectus  is  amended  and  restated  in its
entirety to read as follows:

     Citadel Equity Fund Ltd.,  Continental  Assurance  Company on Behalf of its
Separate Account (E), DBAG London,  Prudential  Insurance Co. of America and UBS
AG London Branch are affiliates of registered broker-dealers,  and each of these
selling  securityholders  has informed us that (1) such  selling  securityholder
purchased its notes in the ordinary course of business,  and (2) at the time the
notes were purchased,  the selling  securityholder  had no agreements,  plans or
understandings, directly or indirectly, to distribute the notes or the shares of
common stock issuable upon conversion of the notes.

                               -------------------




     The section of the prospectus  entitled "Selling  Securityholders" on pages
21-22 of the  prospectus  is amended  and  restated  in its  entirety to read as
follows:

                             SELLING SECURITYHOLDERS

     We issued the notes covered by this  prospectus  in a private  placement on
June 23,  2003.  The notes were resold by the initial  purchasers  to  qualified
institutional   buyers  under  Rule  144A  under  the  Securities  Act.  Selling
securityholders,   including  their  transferees,   pledgees,  donees  or  their
successors, may offer and sell the notes and shares of our common stock issuable
upon conversion of the notes pursuant to this prospectus.

     The  following  table sets forth  information  with  respect to the selling
securityholders and the principal amount of notes and shares of our common stock
issuable  upon  conversion  of the  notes  beneficially  owned  by each  selling
securityholder  that may be offered  pursuant to this  prospectus.  The table is
based on information given to us by selling securityholders on or before June 3,
2004.




                                                                   Shares of
                                                                   DoubleClick                           Shares of
                                                  Principal          Common                             DoubleClick
                                                  Amount of           Stock                            Common Stock
                                                    Notes         Beneficially       Notes Owned        Owned After
                                                Beneficially       Owned Upon           After          Completion of
                                                 Owned That       Conversion of     Completion of      the Offering
Name of Securityholder                           May Be Sold      the Notes (1)    the Offering (2)       (2)(3)
- -------------------------------------------      ------------     -------------    ----------------    -------------
                                                                                                
Arkansas PERS..............................         1,300,000          99,100             0                 0

Barclays Global Investors Diversified
Alpha Plus Funds...........................           291,000          22,183             0                 0

Citadel Equity Fund Ltd....................        25,635,000       1,954,184             0                 0

CNH CA Master Account, L.P.................         1,000,000          76,231             0                 0

Continental Assurance Company on
Behalf of its Separate Account (E).........           600,000          45,738             0                 0

DBAG London................................           250,000          19,057             0                 0

Forest Fulcrum Fund LP.....................           759,000          57,859             0                 0

Forest Global Convertible Fund, Ltd.,
Class A-5..................................         2,818,000         214,819             0                 0

Forest Multi-Strategy Master Fund SPC,
on Behalf of its Multi-Strategy Segregated
Portfolio..................................         1,033,000          78,746             0                 0

JMG Triton Offshore Fund, Ltd..............        14,000,000       1,067,235             0                 0

KBC Financial Products USA Inc.............         1,150,000          87,665             0                 0

LDG Limited................................           471,000          35,904             0                 0

Lexington Vantage Fund c/o TQA
Investors, L.L.C...........................           140,000          10,672             0                 0

LLT Limited................................           260,000          19,820             0                 0

Lyxor Forest Fund Ltd......................         1,278,000          97,423             0                 0

Nuveen Preferred and Convertible Fund
JQC........................................         5,750,000         438,328             0                 0

Prudential Insurance Co. of America........           110,000           8,385             0                 0

Relay 11 Holdings Co.......................           185,000          14,102             0                 0

Sphinx Convertible Arbitrage SPC...........           108,000           8,232             0                 0

Sphinx Fund c/o TQA Investors, L.L.C.......           272,000          20,734             0                 0

                                      S-2




                                                                   Shares of
                                                                   DoubleClick                           Shares of
                                                  Principal          Common                             DoubleClick
                                                  Amount of           Stock                            Common Stock
                                                    Notes         Beneficially       Notes Owned        Owned After
                                                Beneficially       Owned Upon           After          Completion of
                                                 Owned That       Conversion of     Completion of      the Offering
Name of Securityholder                           May Be Sold      the Notes (1)    the Offering (2)       (2)(3)
- -------------------------------------------      ------------     -------------    ----------------    -------------

State of Oregon/Equity.....................         5,800,000         442,140             0                 0

TQA Master Fund, Ltd.......................         7,308,000         557,096             0                 0

TQA Master Plus Fund, Ltd..................         7,214,468         549,966             0                 0

UBS AG London Branch.......................        16,000,000       1,219,697             0                 0

Univest Convertible Arbitrage Fund Ltd.....           169,000          12,883             0                 0

Xavex - Convertible Arbitrage 4 Fund.......             99,000           7,546             0                 0

Xavex - Convertible Arbitrage 7 Fund c/o
TQA Investors, L.L.C.......................          1,278,000          97,423             0                 0

Zurich Institutional Benchmarks Master
Fund, Ltd. c/o TQA Investors, L.L.C........          1,002,000          76,383             0                 0

- -----------------

(1)  Assumes  conversion  of all of the  selling  securityholders'  notes at the
     maximum  conversion rate of 76.2311 shares per note.  However,  the maximum
     conversion rate is subject to adjustment as described under "Description of
     the  Notes-Conversion  Rate Adjustments." As a result, the amount of common
     stock issuable upon conversion of the notes may increase or decrease in the
     future.

(2)  We do not know when or in what amounts a selling  securityholder  may offer
     notes or shares of our common stock  issuable upon  conversion of the notes
     for  sale.  The  selling  securityholders  might not sell any or all of the
     notes or shares of our common stock  issuable upon  conversion of the notes
     offered by this prospectus.  Because the selling  securityholders may offer
     all or some of the  notes or  shares  of our  common  stock  issuable  upon
     conversion of the notes  pursuant to this  offering,  and because there are
     currently no agreements, arrangements or understandings with respect to the
     sale of any of the  notes or  shares  of our  common  stock  issuable  upon
     conversion  of the  notes,  we cannot  estimate  the number of the notes or
     shares of our common stock issuable upon  conversion of the notes that will
     be  held  by  the  selling  securityholders  after  the  completion  of the
     offering.  However, for purposes of this table, we have assumed that, after
     completion of the offering, none of the notes or shares of our common stock
     issuable upon  conversion of the notes covered by this  prospectus  will be
     held by the selling securityholders.

(3)  Assumes  that any  other  holders  of  notes,  or any  future  transferees,
     pledgees,  donees or successors of or from any such other holders of notes,
     do not  beneficially  own any  shares of our  common  stock  other than the
     shares of our common stock issuable upon conversion of the notes.

Information  about  other  selling  securityholders  will  be  set  forth  in an
amendment to the registration statement of which this prospectus is a part or in
prospectus amendments or supplements, as required.

None of the selling securityholders has held any position or office with, or has
otherwise had a material relationship with, us or any of our subsidiaries within
the past three years.

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             The date of this prospectus supplement is June 3, 2004.

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