The influence of reaction parameters such as temperature, contact time, and O2, CO, H2, CO2, and H2O partial pressures on the catalytic performances of 4 wt % CuO/CeO2 in the CO-PROX process (the preferential oxidation of CO) has been investigated in a fixed-bed reactor. Catalyst appears very active (light-off at 70 C) and selective; reaction kinetics is weakly depressed by CO2 and H2O and not significantly increased with increasing O2 concentration, while the reaction order in CO is variable with temperature ranging from values <1 up to 110 C and >1 at higher temperatures. A power-law rate equation fitted the experimental data under typical CO-PROX conditions in order to evidence the lower activation energy of the catalytic oxidation of CO with respect to H2. A Langmuir-Hinshelwood type reaction rate is able to describe the catalytic behavior in the whole field of experimental conditions explored.