Exhibit 8.1

                                                      FIRM and AFFILIATE OFFICES
                                        DUANE  MORRIS
                                                       NEW YORK
                                                       LONDON
                                                       CHICAGO
                                                       HOUSTON
                                                       PHILADELPHIA
                                                       SAN FRANCISCO
                                  July 21, 2004        BOSTON
                                                       WASHINGTON, DC
                                                       ATLANTA
                                                       MIAMI
                                                       NEWARK
                                                       ALLENTOWN
                                                       WILMINGTON
                                                       CHERRY HILL
                                                       HARRISBURG
                                                       BANGOR
                                                       PRINCETON
                                                       PALM BEACH
                                                       WESTCHESTER

F.N.B. Corporation
One F.N.B. Boulevard
Hermitage, Pennsylvania  16148

         Re: Agreement and Plan of Merger pursuant to which Slippery Rock
             Financial Corporation will merge with and into F.N.B. Corporation

Ladies and Gentlemen:

      We have acted as counsel to F.N.B. Corporation, a Florida corporation
("FNB"), in connection with the proposed merger (the "Merger") of Slippery Rock
Financial Corporation, a Pennsylvania corporation ("Slippery Rock"), with and
into FNB, pursuant to the terms of and as described in that certain Amended and
Restated Agreement and Plan of Merger dated as of July 15, 2004 (the "Merger
Agreement") between FNB and Slippery Rock. At your request, and as contemplated
by the Merger Agreement, we are rendering our opinion concerning certain federal
income tax consequences of the Merger. Unless otherwise indicated, all
capitalized terms used in this opinion have the same meaning as used in the
Merger Agreement.

      For the purpose of rendering our opinion herein, we have conducted an
examination of the Internal Revenue Code of 1986, as amended (the "Code"), and
such other applicable laws, regulations, rulings, decisions, documents and
records as we have deemed necessary. With respect to factual matters, we have
relied upon the Merger Agreement, including, without limitation, the
representations of the parties set forth therein, Amendment No. 1 to Form S-4
Registration Statement (File No. 333-116526) filed with the Securities and
Exchange Commission in connection with the transactions described herein (the
"Form S-4"), and upon certain statements and representations made to us in
certificates by officers of FNB and Slippery Rock (the "Representation
Letters"), in each case without independent verification thereof. With the
consent of FNB, we have relied on the accuracy and completeness of the



F.N.B. Corporation
Page 2
July 21, 2004

statements and representations contained in the Representation Letters, the
Merger Agreement and the Form S-4 and have assumed that each will be complete
and accurate as of the Effective Time. We have assumed that any representation
or statement qualified by "to the best of knowledge" of the party making such
representation or statement, or by any similar expression, is correct without
such qualification. As to all matters in which a person or entity making a
representation referred to above has represented that such person or entity
either is not a party to, or does not have, or is not aware of, any plan,
intention, understanding or agreement, we have assumed that there is in fact no
such plan, intention, understanding or agreement with respect to such matters.

      For purposes of this opinion, we have assumed that (i) the Merger will be
consummated according to the Merger Agreement and (ii) the Merger will qualify
as a statutory merger under applicable state law.

      Based on the foregoing, and subject to the qualifications set forth below,
we are of the opinion that under the Code the Merger will constitute a
reorganization under Code Section 368(a), and FNB will be a party to the
reorganization within the meaning of Code Section 368(b). In addition, although
the discussion set forth in the Form S-4 Registration Statement under the
heading "Material Federal Income Tax Consequences of the Merger" does not
purport to discuss all possible United States federal income tax consequences
applicable to the Slippery Rock Shareholders as a result of the transactions
provided for in the Merger Agreement, such discussion constitutes our opinion
concerning the material federal income tax consequences applicable to the
Slippery Rock shareholders as a result of the transactions provided for in the
Merger Agreement.

      The opinion expressed herein is based upon our interpretation of existing
legal authorities, and no assurance can be given that such interpretations would
be followed if the exchange of shares contemplated by the Merger became the
subject of administrative or judicial proceedings. Statements of opinion herein
are opinions only and should not be interpreted as guarantees of the current
status of the law, nor should they be accepted as a guarantee that a court of
law or administrative agency would concur in such statement.

      Except as set forth above, we express no opinion with respect to the tax
consequences of the Merger, including without limitation:

      (i)   the appropriate method to determine the fair market value of any
stock or other consideration received in any sale or exchange; or

      (ii)  the state, local or foreign tax consequences of any aspect of the
Merger.

      The opinion set forth herein is addressed only to, and may be relied upon
only by, the addressees hereof, and only in connection with the transactions
contemplated by the Merger Agreement, and are not to be used or relied upon by
any other parties, or in connection with any other transactions, except with our
prior written consent.



F.N.B. Corporation
Page 3
July 21, 2004

      We expressly consent to the filing of this opinion as an exhibit to the
registration statement on Form S-4 filed by FNB with the Securities and Exchange
Commission in connection with the Merger, and to the reference to this opinion
in the proxy statement/prospectus contained in such registration statement.

                                       Very truly yours,

                                       /s/ Duane Morris LLP