By FTIR spectroscopy at variable temperatures it was shown that CO interacts with extraframework alkali or Ca²⁺ cations in zeolites to form both M⋯CO and M⋯OC species that are in a temperature dependent equilibrium. The C-bonded species have always higher adsorption energy and account for the strong high-frequency vCO band, while the O-bonded structures reveal themselves in a weak band shifted to lower wavenumbers with respect to the free CO molecule. The difference between the energies of C- and O-bonded species depends upon the cation, and to some extent on the zeolite framework. These CO reorientation energy values, as well as the frequency shifts are well reproduced by a simple electrostatic model of dipole-cation interaction. For CaY zeolite, where two CO molecules can be adsorbed on the same cation, the presence of O-bonded molecules accounts for additional frequency increase of the adjacent CO, that could be interpreted as adsorption-induced increase of Lewis acidity.