In this study, we investigated the effect of inner electrode structure on methane conversion (X-CH4) and product selectivity using dielectric barrier-discharge plasma. We used two types of inner electrodes: those with discharge disks set at 5 mm intervals (Type A) and those with discharge disks set at 0 mm intervals (Type B). When electric power (Pw) was increased, the methane conversion (X-CH4) of Type A and TYPe B increased. However, the X-CH4 of Type A reactor was lower than that of Type B reactor, irrespective of Pw. When the total thickness of the discharge disks set at 0 mm intervals was the same as that in Type A, X-CH4 was lower than the X-CH4 for Type A or Type B. This result shows that the presence of discharge disk intervals can result in increased X-CH4. The primary product was ethane when using electrodes with/without intervals under various conditions. When Pw was increased in Type A, the product carbon selectivity (PCS) of propane and C4+ hydrocarbon increased with increased Pw and the PCS of ethylene decreased. When lype B was used, the PCS of acetylene also increased with an increase in Pw. These results show that Type A reactors can promote homologation and Type B reactors can promote dehydration. When the flow rate (F-0) was varied at a Pw of 3 or 32W, X-CH4 decreased with increased F-0. Ethane was again the primary product, and the F-0 value did not dramatically affect the PCS. (c) 2015 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers.