Exhibit 16.1 [LETTERHEAD OF GRANT THORNTON] June 21, 2005 U.S. Securities and Exchange Commission Office of the Chief Accountant 100 F Street, NE Washington, DC 20549 Re: Westbank Corporation File No. 0-12784 Dear Sir or Madam: We have read Item 4.01 of Form 8-K of Westbank Corporation dated June 16, 2005, and agree with the statements concerning our Firm contained therein. Very truly yours, /s/ Grant Thornton LLP - ---------------------- cc: Richard A. Schaberg, Esq. Partner Thacher Proffitt & Wood 1700 Pennsylvania Avenue NW Suite 800 Washington, D.C. 20006