The effect of Ce addition to alumina-supported copper, cobalt, and copper-cobalt oxides with low loadings on the catalysts efficiency in NO reduction with CO was studied. The attention was focused on varying the impregnation procedure in the ternary-supported catalysts in order to determine the best catalyst as well as the reasons for the enhanced catalytic activity. Ternary Co-Cu-Ce and binary Co-Ce, Cu-Ce, and Cu-Co-supported alumina were prepared and characterized by ICP, XRD, TEM, adsorption studies, XPS, H-2-TPR, and catalytic investigations. The high activity of the ternary and the binary catalysts was determined by the favorable influence of the added cerium on the dispersion of the copper and cobalt active phases. The presence of ceria contributes to the formation of appropriate active phases, resulting in catalytic sites on the surface of the samples that promote the reduction of NO with CO. (C) 2010 Elsevier Inc. All rights reserved.