In this study, the effect of water vapor on NOx storage and reduction in combination with non-thermal plasma was investigated. The results indicated that H2O could lower NOx adsorption capacity of H-ZSM-5 at the adsorption stage, due to the competitive adsorption between H2O and NOx on the surface of H-ZSM-5. When the content of H2O was above 2%, the NOx breakthrough adsorption capacity of H-ZSM-5 remained stable at 2.0 mL g(-1). At the discharge stage, the introduction of H2O decreased the total NOx conversion from 98.7% to 94.2%, while the conversion of adsorbed NOx to N-2 from 94.0% to 83.9%. When increasing the CH4 concentration and the discharge power, the total NOx conversion and the conversion of adsorbed NOx to N-2 moved up to 99.5% and 97.4%, respectively. In addition, although Ni-ZSM-5 exhibited better resistance to H2O than H-ZSM-5 for NOx adsorption, it showed inferior efficiency for NOx removal and nearly 15% NOx remained after the discharge stage. (C) 2013 Elsevier B.V. All rights reserved.