Present study investigated the effect of catalyst placement in the discharge zone on the plasma-catalytic oxidation of NO to NO2. The TiO2 powder catalyst was placed either to the inlet or outlet of the reactor and the results were compared with the results obtained when the catalyst covered the full length of the reactor or was totally absent. The long-term oxidation was improved by the catalyst only when the catalyst was present in the outlet of the reactor or on full length of the reactor. The catalyst placement influenced also adsorption related transient changes of NO and NO2 concentrations in the outlet of the reactor. The observed results can be explained by the increased importance of forward reactions resulting in the oxidation of NO to NO2 in the presence of catalyst. [GRAPHICS] .