||When La and/or Ce were added to Pd/(-Al2O3, better activity for NO, CO and C3H6 was taken. It was shown by the results of BET, chemisorption, XRD and XPS that La-promoted one had a good thermal resistance, relatively a high dispersion of Pd, suppressed the reaction to the (-Al2O3, and kept the binding energy of Pd species constant. Such roles of La can be explained by the model that Pd particles are decorated by amorphous LaOx species. XPS spectra showed that Pd species in the fresh state existed as PdO state. After aging Pd species became surface-deficient, whereas the element of O, Al, La and Ce became surface-abundant. This process and the transition to (-Al2O3 phase can be suggested to be main deactivation processes.