Catalytic performance of Cu/CeO2 catalysts was studied as a function of Cu loading in the oxidative steam reforming of methanol (OSRM) reaction. The reduction of CuO/CeO2 catalysts evidenced the existence of different kinds of CuO species. Their reduction peaks shift to higher temperatures as a function of the CuO loading. The catalyst which exhibited a reduction peak at 242 degrees C showed low activity on the OSRM reaction and poor H-2 selectivity. SEM, XRD and TPR analyses of this sample revealed the strong influence of the large crystallites of Cu on the catalyst performance. Catalysts with 2 and 6wt% of copper showed a similar activity in the OSRM reaction. However, the highest H-2 selectivity was observed on the 2Cu/CeO2 catalyst in the range of 210-230 degrees C. Above 230 degrees C, H-2 selectivity was improved on the 6Cu/CeO2 sample and decreased in the 2Cu catalyst. A diminished H2 selectivity is attributed to the loss of the active copper phase by oxidation during catalytic reaction, as confirmed by TPR and EPR studies on the 2Cu catalyst after catalytic reaction. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.