In order to investigate the effect of transition metal addition to platinum with different support materials on preferential CO oxidation, structure and chemical properties of supported bimetallic catalysts prepared by electron beam irradiation method were correlated to the catalytic performance. On Al2O3, decoration of Pt by small amount of Co (Co/Pt similar to 0.03) drastically increased CO and O-2 conversions while addition of equimolar Cu to Pt increased them only above 100 degrees C, where the rate-controlling factor was suggested to change from oxygen transport to CO activation. On CeO2, either addition of Co or Cu to Pt had minor or negative effect on high O-2 conversion inherent to high oxygen transport at Pt-CeO2 interface. On Pt-Cu/CeO2, however, metal-CuOx interface dominates the reaction characteristics to give improved selectivity, which is suitable for deep CO removal in excess O-2/CO condition. The order of selectivity above 100 degrees C, Pt-CoOx > Pt(alloy)-CuOx > Pt-CeO2 interfaces, was derived from structural analysis and catalytic tests. Copyright (c) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.