In this work, the epoxidation of ethylene under a cylindrical dielectric barrier discharge (DBD) reactor and a parallel DBD reactor was comparatively studied. The effects of important operating parameters-feed O 2 /C 2 H 4 molar ratio, applied voltage, input frequency, and residence time-were investigated on the reaction performance in terms of reactant conversions, product selectivities, product yields, and power consumptions per molecule of ethylene converted and per molecule of ethylene oxide produced. The optimum conditions obtained from the operating parameter investigation were used for a comparative performance evaluation of both DBD reactor systems. It was found that under the optimum conditions of each system, the cylindrical DBD system exhibited superior epoxidation performance for ethylene oxide production compared to the parallel DBD system, indicating that the electrode geometry (electrode edge length-to-electrode surface area ratio) plays a significant role in the ethylene epoxidation.