From isotope oxygen exchange reactions and simulations of these experiments, the important steps in oxygen transport in Pt/ceria were distinguished and their rates were estimated. A Pt/alumina sample was also experimentally investigated for comparison, Oxygen surface diffusion as well as oxygen spillover from Pt to ceria was found to be fast in comparison with adsorption/desorption of oxygen on the metal and oxygen bulk diffusion. The exchange rate was found to be higher on a very-low-Pt-dispersion sample than on a high-dispersion sample, which in the model was explained by the different adsorption properties of oxygen.