Electrochemical and chemical reactions of CO2 with H-2 in a gas phase were studied in an attempt to synthesize hydrocarbons by plasma reactions. When plasma was fired in a CO2 gas alone, the only product detected was CO, showing that the chemical decomposition of CO2 is dominant in the plasma phase. When H-2 was guided into the reaction chamber, hydrocarbons such as methane (CH4), ethylene (C2H4), and ethane (C2H6) could be produced. Hydrocarbon formation was found to be more effective on the Cu electrode than on the Fe electrode, implying that an electrode material and then the electrode reactions can also affect the plasma reaction taking place among highly excited species. Hydrocarbons were effectively formed when the flow rate of H-2 to CO2 exceeded three, in accordance with the expected chemical formulas of hydrocarbon formation.