The selective reduction of NO by C3H8 is performed on copper-based catalysts : Cu/Al2O3, Cu/SiO2, Cu/SiO2-Al2O3 solids, fresh and hydrothermally-treated Cu-MFI with various Si/Al ratios. For all the Cu-MFI solids and for the non-zeolitic supported-copper solids with low copper loadings, O-2 promotes the reduction of NO. The C3H8-NO reaction rate correlates with the number of accessible and isolated Cun+ ions deduced from the infrared spectroscopy of adsorbed CO. When only one type of sites is detected, the FTIR spectroscopy of adsorbed CO allows an estimation of the copper dispersion.