A total of 10 noble metal (Rh, Pt, Pd, Ru and It) catalysts, either supported on CeO2 or Ce0.63Zr0.37O2, were prepared. Catalysts were fully characterized using XRD, N-2 adsorption at -196degreesC, TEM and H-2 chemisorption. Oxygen storage processes were carefully investigated. The influence of temperature was checked and a key role of oxygen diffusion was further demonstrated. A review of the reactions involved in the CO transient oxidation reaction is finally proposed.