The hydrogenation of CO2 to hydrocarbons over precipitated iron catalysts was carried out in a stirred tank slurry reactor. Effects of potassium promotion and structural promotion using Al2O3 :or SiO2 on the activity and selectivity were investigated with the co-precipitated Fe-Cu-Al (or Si)-K catalytic system. Also, tha-reaction performance in the slurry reactor was compared: with that in a fixed-bed reactor. The addition of either Al2O3 or SiO2 by the mixing method gave hardly any improvement in the catalytic activity or selectivity in CO2 hydrogenation. Instead, the addition of SiO2 by the mixing method lowered the selectivities to long-chain hydrocarbons and olefins, However, the addition of Al2O3 by co-precipitation increased CO2 conversion as well as the selectivity to C2+ hydrocarbons, but decreased the selectivity to CO. The addition of potassium promoted the CO2 hydrogenation activity and the selectivity to hydrocarbons, shifted the product distribution to the direction of olefins and long-chain hydrocarbons, In terms of CO2 conversion and hydrocarbon selectivity, K/Fe = 6/100 is the optimum K level at the-conditions employed in the present study. The comparison of slurry and fixed-bed reactors showed that the slurry reactor was not as favorable as the fixed-bed reactor for CO2 hydrogenation,