Pt nanoparticles are successfully deposited on wormholelike mesoporous carbons (WMCs) using a pulse microwave-assisted polyol method. WMCs with two different pore diameters are used. The particle size of Pt on both supports is identical, about 3 nm. It has been found that Pt utilization efficiency is very low when the pore diameter of WMCs (D-p) is equal to the diameter of Pt nanoparticles (D-Pt). However, in the case that D-p is more than twice D-Pt, the electrochemical surface area and Pt utilization efficiency are dramatically enhanced, and in turn, hydrogen electrooxidation activity is greatly improved. (C) 2009 Elsevier B.V. All rights reserved.