In this work, 10 wt% Pt-Ru/C alloy catalysts with and without CeO2 modification were prepared by wet chemistry and physically characterized by transmission electron microscopy, X-ray diffraction, and inductively coupled plasma-atomic emission spectrometry. The catalytic activity of the prepared catalysts toward anodic oxidation of methanol was examined by cyclic voltammetry (CV). Modification of the Pt-Ru/C catalyst with CeO2 significantly increased current densities measured by CV. The promotion was attributed to an increased dispersion of alloy particles. However, the extent of promotion depended heavily on the method of catalyst preparation. Evidently, some of the alloy particles did not participate in reaction because they were impregnated into internal pores of carbon support or occluded into the bulk of CeO2 crystallites codeposited. Accordingly, the anode activity of prepared catalysts should be proportional to the dispersion of alloy particles dispersed and to their accessibility to reactant during reaction. A promoted catalyst with the highest exposure of Pt-Ru nanoalloys exhibited the best electroactivity to methanol oxidation. (c) 2006 Elsevier Inc. All rights reserved.