This paper presents a study of the electrocatalysis of ethanol oxidation reactions in an acidic medium on Pt-CeO2/C (20 wt.% of Pt-CeO2 on carbon XC-72R), prepared in different mass ratios by the polymeric precursor method. The mass ratios between Pt and CeO2 (3:1, 2:1, 1:1, 1:2, 1:3) were confirmed by Energy Dispersive X-ray Analysis (EDAX). X-ray diffraction (XRD) structural characterization data shows that the Pt-CeO2/C catalysts are composed of nanosized polycrystalline non-alloyed deposits, from which reflections corresponding to the fcc (Pt) and fluorite (CeO2) structures were clearly observed. The mean crystallite sizes calculated from XRD data revealed that, independent of the mass ratio, a value close to 3 nm was obtained for the CeO2 particles. For Pt, the mean crystallite sizes were dependent on the ratio of this metal in the catalysts. Low platinum ratios resulted in small crystallites. and high Pt proportions resulted in larger crystallites. The size distributions of the catalysts particles, determined by XRD, were confirmed by Transmission Electron Microscope (TEM) imaging. Cyclic voltammetry and chronoamperometic experiments were used to evaluate the electrocatalytic performance of the different materials. In all cases, except Pt-CeO2/C 1:1, the Pt-Ceo(2)/C catalysts exhibited improved performance when compared with Pt/C. The best result was obtained for the Pt-CeO2/C 1:3 catalyst, which gave better results than the Pt-Ru/C (Etek) catalyst. (C) 2009 Elsevier B.V. All rights reserved.