The stoichiometric NO-CO reaction was studied over Cu/CeO2 catalysts prepared with different Cu loadings and specific surface areas of CeO2 to investigate the relationship between catalytic activity and the copper-ceria interaction. XRD, ESR and H-2-TPR results revealed that CuO species interacted with CeO2 in three structurally different forms: isolated Cu2+, a highly dispersed CuO film, and large CuO particles. The CuO film showed a higher NO-CO reaction activity than the other species. An Operando XAFS study revealed that the reduction of the CuO film during the NO-CO reaction occurred at the Cu-O-Ce interface. Thus, we concluded that the most suitable CuO structure to effectively exploit Cu-O-Ce interface sites in the NO-CO reaction is a two-dimensionally dispersed CuO film. (C) 2015 Elsevier B.V. All rights reserved.