The non-thermal plasma (NTP) technique, which suffers from low selectivity in complete oxidation o volatile organic compounds to CO2 and H2O, creates unwanted and harmful byproducts. NTP in concer with photocatalyst can resolve this limitation due to additional oxidation. TiO2 and ZnO nanoparticle light. In this study, to compare the performance of NTP and the combined system, chlorobenzene remova selectivity of CO2 and byproducts formation were investigated. The results showed that the combine system enhanced both the removal efficiency and CO2 selectivity. The output gas of the NTP reacto contained chlorobenzene, phosgene, O3, NO, NO2, CO, CO2, HCL and CL. The bulk of these byproducts wa oxidized on the surface of the nanocomposite; as a result, the content of the byproducts in the output ga of the combined system decreased dramatically. The removal efficiency and CO2 selectivity increased b rising the applied voltage and residence time because the collision between active species and pollutan molecules increases. Based on these results, the combined system is preferred due to a higher performanc and lower formation of harmful byproducts.were coated on the surface of the expanded graphite and placed downstream of the NTP reactor under UV