The methanation of CO2 gas at 200 degrees C was investigated in Co(II) or Ni(II)-bearing ferrites with substitution of up to 0.262 and 0.143, respectively. The metal substitution in the ferrite facilitated the methanation of the deposited carbon from CO2 gas in the H-2-reduced M(II)-bearing ferrite in comparison with the reactivity of the H-2-reduced magnetite with the same spinel structure. The effect on the reactivity of methanation was found to be much larger in Ni(II)-substitution. The degree of the effect increased with increases in the Ni(II)-substitution, while it remained about the same with increases in the Co(II) -substitution. The maximum methanation (86.9%) of CO2 was attained in the Ni(II)-bearing ferrite activated by H-2 gas for 3.0 h.