EXHIBIT 32.2

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

          In connection with the Quarterly Report on Form 10-Q of DoubleClick Inc. (the “Company”) for the period ended March 31, 2005 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned, Bruce Dalziel, Chief Financial Officer of the Company, hereby certifies, pursuant to 18 U.S.C. Section 1350, that:

      (1) the Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

      (2) the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ BRUCE DALZIEL

Bruce Dalziel

Chief Financial Officer

Dated: May 10, 2005