<Page>

                                                             Exhibit 99.906 CERT

                                    EHIBIT 3
         CERTIFICATION PUSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT

     Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, each of the
undersigned officers of H&Q HEALTHCARE INVESTORS, do hereby certify, to such
officer's knowledge, that the report on Form N-CSR of H&Q LIFE SCIENCES
INVESTORS for the year ended September 30, 2004 fully complies with the
requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934,
as applicable, and information contained in the Form N-CSR fairly presents, in
all material respects, the financial condition and results of operations of H&Q
LIFE SCIENCES INVESTORS for the stated period.
           /s/ Daniel R. Omstead                   /s/ Kimberley L. Carroll
           --------------------------              ---------------------------
               Daniel R. Omstead                       Kimberley L. Carroll
           Title: President                        Title: Treasurer


Date: December 9, 2004
      ----------------


A signed  original of this written statement required by Section 906 has been
provided to H&Q LIFE SCIENCES INVESTORS and will be retained by H&Q LIFE
SCIENCES INVESTORS and furnished to the SEC or its staff upon request. This
statement accompanies this report on Form N-CSR pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002 and shall not be deemed as filed by H&Q LIFE SCIENCES
INVESTORS for purposes of the Securities and Exchange Act of 1934.