Velocity distributions of desorbing product CO 2 in CO oxidation on Pt(133) were analyzed in both the active and inhibited regions at the steady state. The translation temperature is high in the active region where the reaction is in the first order with respect to CO. It decreases sharply with increasing CO pressure when the reaction shifts to the inhibited region where CO retards the reaction. The translational energy of CO 2 increases linearly with the surface temperature.