Cobalt oxide catalysts deposited on titania–ceria supports were examined in deep ethanol oxidation and N2O decomposition. Supports with various molar ratio of CeO2/TiO2 were prepared by the sol–gel method and cobalt components were introduced by impregnation and subsequent calcination. The supports and catalysts were examined by chemical analysis, X-ray diffraction, nitrogen physisorption, H2-TPR, and NH3-TPD. It was found out that the ethanol conversion at 200 °C is proportional to the CeO2/(CeO2 + TiO2) molar ratio in the supports, and temperature T 50 of ethanol oxidation is proportional to the amount of components reducible in the temperature range of 20–500 °C. A comparison of specific catalytic activities in both ethanol oxidation and N2O decomposition proved a lower rate of N2O decomposition than that of oxidation of ethanol (approximately 25 times). The findings confirmed the great importance of the supports surface areas on specific activity of cobalt catalysts in both reactions. The obtained results showed that ceria is the best support of cobalt oxides for both deep ethanol oxidation and N2O decomposition when reaction rates are related to unit amount of active component in the catalysts.