By using a combination of oxygen buffering capacity (OBC) and oxygen storage capacity (OSC) measurements, the redox behaviour of a Pt/CeToO(x) catalyst is compared to that of a classic model TWC system: Pt/CeO2. The results reported here show that the redox efficiency of the Pt/CeTbOx catalyst is much better, especially at low temperature operation conditions such as those occurring during the cold start of engines. The catalyst containing terbium also shows lower ＇light-off temperatures for both methane and carbon monoxide oxidation.