This work investigated influence of cerium modification methods (impregnation and ion-exchange) on the gold dispersion, surface chemical states, synergistic effect between gold and cerium and CO oxidation activity of Au catalysts supported on Ce modified mordenites. The supports and catalysts were characterized by XRF, ICP, XRD, N-2 adsorption-desorption, UV-vis spectroscopy, HRTEM, in situ FT-IR and XPS. In general, Ce-containing Au catalysts were found to be more active in CO oxidation than the Ce-free counterpart, with the impregnation method of cerium modification being more effective than the ion exchange method. The different catalytic performance of Ce-containing catalysts was related to multiple factors: (1) the impregnation method of cerium modification was more favorable to form Au particles with smaller mean size than the ion-exchange method, due to the higher ratio of surface Lewis acid sites; (2) the interface between Au and CeO2 particles produced by impregnation method was more beneficial for the redox equilibrium of Au-0 + Ce4+ <-> Au3+ + Ce3+ to shift to right to form more active Au3+ species than the interface between Au particles and Ce cations produced by ion-exchange method, which enhanced the synergistic effect between gold and cerium and the catalytic performance of CO oxidation. (C) 2012 Elsevier B.V. All rights reserved.