Ab initio calculations were performed to simulate the interaction between CO or NO and copper-containing zeolite at the SCF level. The zeolite catalysts were modelled by a molecular cluster of composition H8Si3AlO4Cudelta+ with delta = 0, 1. For delta = 0 the oxidation state of the Cu atom corresponds to 1+ in Cu+/zeolite, while for delta = 1 it is equal to 2+ in Cu2+/zeolite. It was found that only Cu+/zeolite should be responsible for CO and NO adsorption from the gas phase. The calculated heats of adsorption compare well with available experimental data and together with adsorption geometries allow us to interpret the observed IR data.