Dielectric barrier discharge (DBD) was investigated for the simultaneous removal of NO and SO2 from flue gas in a coal-combustion power plant. The DBD equipment was used in either a mode where flue gas was directed through the discharge zone (direct oxidation), or a mode where produced ozonized air was injected in the flue gas stream (indirect oxidation). Removal efficiencies of SO2 and NO for both methods were measured and compared. Oxidation of NO is more efficient in the indirect oxidation, while oxidation of SO2 is more efficient in the direct oxidation. Addition of NH3, has lead to efficient removal of SO2, due to thermal reaction, and has also enhanced NO removal due to heterogeneous reactions on the surface of ammonium salt aerosols. In the direct oxidation, concentration of CO increased significantly, while it maintained its level in the indirect oxidation. (C) 2010 Elsevier B.V. All rights reserved.