A Pt/CeO2 catalyst has been evaluated for CO oxidation, both in the absence of H-2 and in H-2-rich feedstreams. The catalyst shows high activity and selectivity at temperatures as low as 80 degrees C, what makes it a viable catalyst for the selective depletion of CO in the temperature range at which PEMFC operate. The effect of: oxygen excess during operation (lambda), the presence of either CO2 (5%), H2O (5%) or both in the feedstream, and the spatial time, on catalyst activity and selectivity has been evaluated. A lambda value of at least 2.25 was required for achieving total CO conversion, which occurs in the temperature range of 80-100 degrees C, being the selectivity practically stable at 44%. The presence of CO2 slight activates the catalyst, while steam inhibits catalyst activity. Water gas shift reaction contribution to CO oxidation was checked to be negligible in the 25-200 degrees C range. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.