Hydrogenation of CO2 to hydrocarbons over iron catalysts reduced with hydrogen at 350 degrees C and 500 degrees C has been compared with that of CO. The space time yield of hydrocarbons from CO2 at 250 degrees C is significantly lower than from CO and the selectivity to olefin compounds is also lower from CO2. During the reaction with CO, chi-Fe2.2C is formed, and the surface, which is oxidized even after the reduction at 500 degrees C, is further reduced. On the other hand, formation of the carbide species is slight in hydrogenation of CO2 while the surface is Father oxidized. The formation of the carbide species, which is probably the active site of hydrocarbon formation, is suppressed in the presence of CO2.