CO2 reforming of methane ( CH4) and propane (C3H8) was performed with a silent discharge reactor (SDR). The reactor performance was evaluated in terms of energy efficiencies for the conversion of the substrates and formation of H2 and CO. The reactivity of C3H8 was 2- to 3-fold higher than that of CH4, and both of CH4 and C3H8 were reformed in the order of 1016 molecules/J at 298 K. The energy efficiencies for the conversion of these substrates increased with their initial concentrations, but decreased with an increase in reactor energy density. On the other hand, the energy efficiencies for the conversion of CO2, which were not affected by the hydrocarbon types, were lower than those for the hydrocarbon substrates. A positive temperature effect was observed in the conversion of the hydrocarbon substrates only at low reactor energy densities from 298 to 433 K.