Hard-templated NiO-CeO2 samples with increasing Ni/Ce molar ratios, as well as hard-templated CeO2 and NiO oxides, were prepared. All samples were characterized by different techniques as to their chemical composition, structure, morphology, texture, and redox features. They were investigated in the CO methanation reaction after mild reduction pretreatment (H-2 at 400 degrees C for 1 h). Catalytic testing was performed under atmospheric pressure, 300 degrees C and H-2/CO molar ratios of 3.2 or 1.8. In the latter case, runs were carried out also at 200, 250, and 275 degrees C. Almost complete CO conversion and very high CH4 selectivity (up to 94 and 78 mol% at H-2/CO = 3.2 and 1.8, respectively) were obtained at 300 degrees C over the NiCe mixed oxides, with CO2 as byproduct. CH4 selectivity was found to increase with the increase in Ni content. A growth in the size of Ni particles with the same parameter was also observed, suggesting an influence of the crystallite size on methane formation. In spite of its large Ni crystallite size, a lower CH4 selectivity (73 mol%, at H-2/CO = 3.2) was obtained on pure NiO. This was explained by taking into account the role of CeO2 in limiting CO2 formation. (C) 2016 Elsevier B.V. All rights reserved.