The characterization of the coordination geometry of copper ions included within zeolites has been carried out with a combination of in-situ XAFS, photoluminescence, and IR measurements in order to obtain a detailed description of the formation of isolated Cu+ monomers with planar 3-coordinate or linear 2-coordinate geometry in the zeolite channels by thermal treatment under vacuum. The Cu+ ions within the zeolites were found to exist as isolated Cu+ monomers and (Cu+-Cu+) dimers, their relative concentrations strongly depending on the type of zeolite used. With ZSM-5 and mordenite zeolites, most of the copper cations were found to exist as isolated Cu+ monomers, in contrast to the case of the Y-zeolite. CO molecules were adsorbed selectively only on isolated Cu+ monomers, distorting the coordination geometry to form stable one-on-one Cu+-CO complexes.