This work investigated the effects of cerium precursors [Ce(NO3)(3) and (NH4)(2)Ce(NO3)(6)] on the structure, surface state, reducibility and CO oxidation activity of mesoporous CuO-CeO2 catalysts. The catalysts were characterized by TG-DTA, XRD, LRS, N-2 adsorption-desorption, HRTEM, XPS, H-2-TPR and in situ FT-IR. The obtained results suggested that the precursors exerted a great influence on the properties of CuO-CeO2 catalysts: (1) compared with the catalysts from Ce(III) precursor, the derived Ce(IV) precursor catalysts showed smaller grain size, higher BET surface area, narrower pore size distribution, whereas their reducibility and activities were not enhanced. (2) In contrast, the catalysts from Ce(III) precursor without excellent texture displayed high reducibility and activities for CO oxidation due to the high content of Ce3+, following the redox equilibrium of Cu2+ + Ce3+ <-> Cu+ + Ce4+ shifting to right to form more stable Cu+ species, which was the origin of synergistic effect. The synergistic effect between copper and cerium was the predominant contributor to the improved catalytic activities of CuO-CeO2 catalysts, instead of structural properties. (C) 2012 Elsevier B.V. All rights reserved.