August __,1999

Tucker Anthony Cleary Gull
One Beacon Street
Boston, Massachusetts 02108

Ryan, Beck & Co.
220 South Orange Avenue
Livingston, New Jersey 07039

                                                    Re: Westbank Capital Trust I

Ladies and Gentlemen:

               We have acted as special tax counsel to Westbank Corporation, a
Massachusetts corporation (the "Corporation"), and Westbank Capital Trust I, a
business trust formed under the Business Trust Act of the State of Delaware (the
"Trust"), in connection with the Underwriting Agreement (the "Underwriting
Agreement"), among you, as Underwriters, the Corporation and the Trust, relating
to the offering of an aggregate of 1,700,000 of the Trust's Capital Securities,
liquidation amount of $10.00 per capital security (the "Capital Securities"). In
connection with the issuance of the Capital Securities, the Trust is also
issuing Common Securities, liquidation amount of $10.00 per common security (the
"Common Securities" and, together with the Capital Securities, the "Trust
Securities").

               The Trust Securities are to be issued pursuant to the Amended and
Restated Declaration of Trust (the "Declaration") among the Corporation, as
Sponsor, Wilmington Trust Company, as Property Trustee and as Delaware Trustee,
and Donald R. Chase, Gary L. Briggs and John M. Lilly (collectively, as the
"Administrative Trustees"). The sole assets of the Trust will be the Junior
Subordinated Deferrable Interest Debentures due 2029 (the "Junior Subordinated
Debentures") of the Corporation issued pursuant to an indenture (the
"Indenture"), between the Corporation and Wilmington Trust Company, as Debenture
Trustee. Capitalized terms used and not defined herein shall have the respective
meanings set forth in the Underwriting Agreement.

               In connection with this opinion, we have examined originals or
copies, certified or otherwise identified to our satisfaction, of (i) the
Registration Statement as filed by the Company and the Trust with the Securities
and Exchange Commission on August 26, 1999, as amended (the "Registration
Statement");


                                                                         Page 2.

Tucker Anthony Cleary Gull
Ryan, Beck & Co.
August __, 1999

(ii) the certificate of trust of the Trust filed with the Secretary of State of
the State of Delaware on August 25, 1999; (iii) the Declaration (including the
designations of the terms of the Trust Securities annexed thereto); (iv) the
form of certificates evidencing the Capital Securities and the Common
Securities, in each case annexed to the Declaration; (v) the Underwriting
Agreement; (vi) the Indenture and the form of certificate evidencing the Junior
Subordinated Debentures annexed thereto; (vii) the Debenture Subscription
Agreement between the Corporation and the Trust; (viii) the Common Securities
Subscription Agreement between the Corporation and the Trust; (ix) the Capital
Securities Guarantee Agreement between the Corporation as guarantor and
Wilmington Trust Company for the benefit of the Holders of the Capital
Securities; and (x) the Common Securities Guarantee Agreement by the Corporation
as guarantor for the benefit of the Holders of the Common Securities.
Furthermore, we have relied upon the letter of _______, 1999 from the
Corporation to us containing certain representations and upon certain statements
and representations made by officers of the Corporation and others. We have also
examined originals or copies, certified or otherwise identified to our
satisfaction, of such other documents, certificates and records as we have
deemed necessary or appropriate as a basis for the opinion set forth herein.

               In rendering the opinions expressed below, we have participated
in the preparation of the Registration Statement. Our opinion is conditioned on,
among other things, the initial and continuing accuracy of the facts,
information, covenants and representations set forth in the documents referred
to above and the statements and representations made by officers of the
Corporation and others. In our examination, we have assumed the genuineness of
all signatures, the legal capacity of natural persons, the authenticity of all
documents submitted to us as originals, the conformity to original documents of
all documents submitted to us as certified or photostatic copies and the
authenticity of the originals of such documents. We also have assumed that the
transactions related to the issuance of the Capital Securities, the Common
Securities, and the Junior Subordinated Debentures will be consummated in the
manner contemplated by the Registration Statement.

               In rendering our opinion, we have considered the current
provisions of the Internal Revenue Code of 1986, as amended, Treasury
regulations promulgated thereunder, judicial decisions and Internal Revenue
Service rulings, all of which are subject to change, which changes may be
retroactively applied. A change in the authorities upon which our opinion is
based could affect our conclusions. There can be no assurances, moreover, that
any of the opinions expressed herein will be accepted by the Internal Revenue
Service or, if challenged, by a court.

               Based solely upon the foregoing, we are of the opinion that under
current United States federal income tax law, as of the date hereof:

               (i)         The Junior Subordinated Debentures will be classified
                           for United States federal income tax purposes as
                           indebtedness of the Corporation.

               (ii)        The Trust will not be classified for United States
                           federal income tax purposes as an association taxable
                           as a corporation.


                                                                         Page 3.

Tucker Anthony Cleary Gull
Ryan, Beck & Co.
August 25, 1999

               (iii)       Although the discussion set forth in the prospectus
                           included in the Registration Statement under the
                           heading "CERTAIN FEDERAL INCOME TAX CONSEQUENCES"
                           does not purport to discuss all possible United
                           States federal income tax consequences of the
                           purchase, ownership and disposition of Capital
                           Securities, such discussion constitutes, in all
                           material respects, a fair and accurate summary under
                           current law of the material United States federal
                           income tax consequences of the purchase, ownership
                           and disposition of Capital Securities by a holder who
                           purchases Capital Securities upon original issuance.

               For purposes of this letter, we do not express any opinion
concerning any law other than the federal income tax law of the United States.
Furthermore, our opinions are limited solely to the specific questions and
conclusions set forth herein and we express no opinion to any party as to the
tax consequences, whether federal, state, local or foreign, of the issuance of
the Junior Subordinated Debentures, the Capital Securities, the Common
Securities or of any transaction related to or contemplated by such issuance.

               This opinion is furnished to you solely for your benefit in
connection with the offering of the Capital Securities and the Junior
Subordinated Debentures and is not to be used, circulated, quoted or otherwise
referred to for any other purpose or relied upon by any other person without our
prior written consent. We consent to the filing of this opinion as an exhibit to
the Registration Statement and to the reference thereto under the heading
"Certain Federal Income Tax Consequences" in the prospectus which is a part of
the Registration Statement. We disclaim any undertaking to advise you of any
subsequent changes of the facts stated or assumed herein or any subsequent
changes in applicable law.


                                            Very truly yours,

                                            THACHER PROFFITT & WOOD

                                            By:
                                                --------------------------------