We analyze the kinetics of CO electrooxidation on nm-sized supported Pt crystallites exhibiting (1 1 1) and (1 0 0) facets. Specifically, we show how the CO-diffusion-mediated communication between these facets may modify voltammograms observed by using CO stripping voltammetry. The results obtained demonstrate that the reaction kinetics for nm-sized particles can be remarkably different compared to those expected on the basis of simple superposition of the kinetics corresponding to the infinite faces. These findings have implications for interpretation of experimental data and for the design of real catalysts and also have important consequences for the efforts to bridge the so-called structure gaps in electrocatalysis. (C) 2003 Published by Elsevier B.V.