CuMn2O4 prepared by a microemulsion method is employed as support of ceria with different loading level (between 5 and 80 wt.%) and the CO-PROX properties of corresponding catalysts are explored. The catalysts have been characterized by XRD, S-BET measurement, HREM and XEDS, XPS and TPR, which allows establishing a complete model of the structural and chemical characteristics of the catalysts. The characterization results have been correlated with the analysis of CO-PROX catalytic properties performed by means of activity measurements complemented by operando-DRIFTS. Important differences in structural, redox and catalytic properties are detected as a function of the amount of ceria present in the catalyst. These are shown to depend basically on the size of the supported ceria nanocrystals as well as the fact that the increase in the ceria loading gradually increases the interfacial character of surface exposed sites of the support with important implications for the CO-PROX properties of the catalyst. (C) 2017 Elsevier B.V. All rights reserved.