Adsorption behavior of NO and CO as well as their reaction was investigated on cobalt supported zeolite beta (Co/BEA) prepared by solid-state ion exchange (SSIE) and by impregnation (IMP). By temperature programmed desorption (TPD), two NO desorption peaks at 100 and 260℃ were observed over both SSIE and IMP catalysts with complete desorption after 450℃. CO desorbed from SSIE catalyst between 50 and 200℃. In the same temperature interval negligible CO₂ desorption was observed, most likely due to reaction of CO with trace of cobalt oxides. Over IMP catalysts, desorption of CO₂ was found mainly at 500℃. By comparing CO TPD profiles from physical mixtures of cobalt oxides and HBEA, SSIE catalysts most likely contained cobalt cations in zeolite exchange position while IMP catalysts had cobalt in oxidic forms. The SSIE catalysts were active for NO reduction at 400 and 500℃ with a maximum conversion at 500℃. However, the activity in the presence of water and oxygen was low. Water might inhibit the reaction by blocking active sites for NO and CO, while oxygen reacted with CO to form carbon dioxide. The activity of SSIE was better than IMP catalyst.