A Pt/CeO 2 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°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 (λ), the presence of either CO 2 (5%), H 2 O (5%) or both in the feedstream, and the spatial time, on catalyst activity and selectivity has been evaluated.A λ value of at least 2.25 was required for achieving total CO conversion, which occurs in the temperature range of 80–100°C, being the selectivity practically stable at 44%. The presence of CO 2 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°C range.