LoopNet 10-K 2011 FY Annual report

Exhibit 32.1

Section 1350 Certification (CEO)

LOOPNET, INC.

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 Annual Report on Form 10-K of LoopNet, Inc. for the year ended December 31, 2011, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Richard J. Boyle, Jr., Chief Executive Officer, and Chairman of the Board of Directors of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, 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/    Richard J. Boyle, Jr.

Richard J. Boyle, Jr.

Chief Executive Officer, and

Chairman of the Board of Directors

Date: February 24, 2012