Studies were carried out to explore catalytic NO-CO reactions promoted by La-loaded and unloaded Al2O3 supported Pd in both powder and cordierite monolithic honeycomb forms. La introduction significantly enhanced catalytic activity toward the NO-CO reaction. The results of in situ FT-IR studies suggest that the promotion effect of La is a consequence of efficient formation of surface nitrite species and their reactivity upon introduction of CO as a reactant.