KNOW ALL PERSONS BY THESE PRESENTS, that the undersigned hereby constitutes and appoints
Kenneth T. Lamneck, Glynis A. Bryan and Steven R. Andrews his true and lawful attorneys-in-fact and
agents, for him, and in his name, place and stead, in any and all capacities (i) to sign the
Insight Enterprises, Inc. Annual Report on Form 10-K for the fiscal year ended
December 31, 2009
and any and all amendments thereto and (ii) to file the same, with all exhibits thereto and other
documents in connection therewith, with the Securities and Exchange Commission, granting unto said
attorneys-in-fact and agents full power and authority to do and perform each and every act and
thing requisite and necessary to be done in such connection, as fully to all intents and purposes
as the undersigned might or could do in person, hereby ratifying and confirming all that said
attorneys-in-fact and agents, may lawfully do or cause to be done by virtue hereof.
