The interaction of CO 2 with noble metals deposited on ceria surfaces have been studied by temperature-programmed techniques. A transient kinetic study of CO 2 activation and methanation overM/CeO 2 has also been conducted. The mechanism of interaction betweenM/CeO 2 and CO 2 and its activation in the presence of H 2 to CH 4 is strongly influenced by the reduction temperature, regardless of the metal employed. It is suggested that, by increasing the reduction temperature, a progressive reduction of bulk CeO 2 takes place, which is not promoted by the presence of the metal. The interaction mechanism suggested involves activation of CO 2 on a surface Ce 3+ site with formation of CO followed by oxidation of Ce 3+ to Ce 4+ . The presence of oxygen bulk vacancies will create the additional driving force for the reduction of CO 2 to CO and/or surface carbonaceous species which then rapidly hydrogenate to CH 4 over the supported metal.