The effect of added SnO2 and ZrO2 to CuO/Al2O3 catalysts was investigated with reference to the oxygen spillover phenomena in the selective oxidation of carbon monoxide. The TPR and TPO analyses indicated that SnO2 and ZrO2 addition caused oxygen migration and induced the formation of high concentrations of active oxygen species on the SnO2 and ZrO2 surface. The catalytic activities of SnO2 and ZrO2 supported CuO/Al2O3 catalysts were superior to that for CuO/Al2O3 catalysts in the selective oxidation of carbon monoxide. Oxygen, when absorbed to the SnO2 and ZrO2 surface can spill over to the CuO phase and easily react with carbon monoxide. Consequently, the addition of SnO2 and ZrO2 led to significantly improved activities. This can be attributed to the enhanced migration of oxygen to the catalyst surface.