About 20-40 mol% Ni/ZrO2 catalysts doped with Ce and Sm were synthesized by an ultrasound-assisted method and characterized by a number of physico-chemical methods (XRD, HR TEM, BET, XPS). It was demonstrated that the synthesized catalysts had a mesoporous structure, where ca. 10 nm size Ni nanoparticles were incorporated into the rare earth metal modified tetragonal zirconium oxide. The Ni particles formed during the reduction treatment could support the porous structure in the supports, and thus the porous properties of the catalysts were related to the Ni-loading. The maximum porous volume and size were obtained for the catalyst with a 30 mol% Ni loading, which coincidentally exhibited the highest catalytic activity for the methanation of CO2. After an oxidation-reduction pretreatment, the catalytic activity could be further improved. The increase in the catalytic activity was attributed to the formation of additional active centers on the catalysts' surface.