The decomposition of CO2 in a dielectric packed-bed plasma reactor has been studied. It was found that the dielectric properties and morphology of packing dielectric pellets play important roles in the reaction due to their influence on the electron energy distribution in the plasma. The acid-base properties of the packing materials also affect the reaction through the chemisorption of CO2 on basic sites of the materials. Heterogeneous reactions on the solid surfaces of the dielectric materials also play a role in the reaction, which was also confirmed through the investigation of the influence of the discharge length on the reaction. The reverse reaction of CO2 decomposition, the oxidation of CO, was also investigated to further understand the role of dielectric materials in the plasma and their effect on plasma reactions. Both the decomposition of CO2 and the oxidation of CO in non-packed or dielectric packed reactors are first-ordered.