A hydrothermal method employing citric acid as the chelating agent and sodium hydroxide as the precipitating agent, and different copper precursors (nitrate salt and metallic ring) has been applied in this work for the synthesis of atomically dispersed copper-ceria catalysts. These catalysts were evaluated in CO oxidation reaction. Copper ions were finely and atomically dispersed in both catalysts and strong interaction between copper supported species and ceria resulted in a remarkable promotion of the activity, thus playing a crucial role in the achievement of higher performance in contrary to other physicochemical properties such as specific surface area and defects concentrations, which seem to play a minor role.