The effect of the addition of CeO2 or La2O3 on the surface properties and catalytic behaviors of Al2O3-supported Pd catalysts was studied in the steam reforming of methane. The FTIR spectroscopy of adsorbed CO and the Pd dispersion suggest the partial coverage of Pd-0 by ceria or lanthana species. This could lead to the formation of an adduct MPd (x) O (M = Ce or La) at the surface of the metal crystallites. The addition of ceria or lanthana resulted in an increase of the turnover rate and specific rate for steam reforming of methane. One possible explanation if that the Pd-0*Pd delta+O-M interfacial species (M = Ce or La) are oxidized by H2O or CO2, promoting the O* transfer to the metal surface. This could facilitate the removal of C* species from the metal surface, resulting in the increase of specific reaction rate and increase of the accessibility of CH4 to metal active sites.