NO adsorption, at room temperature, has been studied by infrared spectroscopy on copper MFI catalysts with different Si/Al ratios and copper loadings. The relative amount of the overall Cu2+–NO and Cu+–NO complexes has been evaluated for each catalyst, as well as that of the different Cu2+–NO components. ESR spectra have also been recorded in order to check the different Cu2+ coordinations. It clearly appears that square planar copper sites predominate for high Cu/Al catalysts. A comparison with reactivity data, relative to SCR of NO by propene, under an excess of oxygen, strongly suggests that these sites are involved in the considered reaction.