The adsorption and the reactions of nitric oxide on CuY zeolites with copper ions in various states have been studied by IR-spectroscopy. Forms of NO adsorbed on individual Cu2+ ions, on weak and strong magnetic formations, and on Cu+ ions have been observed. Processes of oxidation and reduction of NO to NO2, N2O and N2 occurring on CuY zeolites are discussed. Adsorption of nitrogen on coordinatively unsaturated copper ions has been observed.