CexZr1-xO2 (x=0.1-0.5) mixed oxides were prepared as supports of CuO/CexZr1-xO2 catalysts. They were characterized and used in the selective oxidation of carbon monoxide (CO) in excess hydrogen. An appropriate amount of zirconium incorporated into CeO2 not only increased the mobility of lattice oxygen but also promoted the activity of the selective CO oxidation. The promotion of CO oxidation was weakened as the amount of Zr4+ increased above 10% (1 - x > 0.1). The temperature (T-100) of 7%CuO/Ce0.9Zr0.1O2 for complete conversion was about 10 degrees lower than that of 7%CuO/CeO2 (378 K), and the selectivity achieved was nearly 100%. The activity of the 7%CuO/Ce0.9Zr0.1O2 catalyst was weakened in the feed in the presence Of CO2 and H2O, but the selectivity and stability of the catalyst were maintained. The 7%CuO/Ce0.9Zr0.1O2 catalyst exhibited not only good activity that was comparable with that of the noble metal catalyst of 5%Pt/Al2O3 but also good selectivity of much greater than 5%Pt/Al2O3. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All tights reserved.