Molecular simulations of the sorption and cosorption energetics and siting locations of M(CO)(6) (M = Cr, Mo, W) in faujasitic M’(n)FAU zeolites (n = 0-96, Si/Al = 100-1, extraframework cations M’ = Li+, Na+, K+, Rb+, Cs+, Mg2+, and Ca2+) have been presented in combination with Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Attenuated Total Reflectance (ATR-FTIR), and Raman scattering experimental study at low temperature. From the present Monte Carlo calculations and the earlier and present experimental works a coherent picture of the sorption and the cosorption of M(CO)(6) has been drawn as a function of the Si/Al ratio of the zeolite framework, the cation size, and the cationic site occupancy as well as the coverage of the sorbates. The most favorable siting regions of the completely siliceous FAU zeolite pore space are the windows of the supercages, with intercage and intracage rapid motions of the M(CO)(6) molecules. In aluminated M’(n)FAU zeolites the calculated average energy provides evidence to the contribution of significant site II cation/sorbate interactions whereas the site I,I’ cation/ sorbate and sorbate/sorbate interactions remain weak even at high loading. In M’(56)FAU zeolites with bulky cations (M’ = K+, Rb+, Cs+), the M(CO)(6) molecules are rigidily held within the windows of the supercages to the six octahedral disposed site II cations. The sorption sites are randomly filled from low coverage to saturation. In M’(56)FAU zeolites with small cations (M’ = Li+, Na+), the distribution of positions occupied by M(CO)(6) is located in the vicinity of the windows. It is suggested that M(CO)(6) is predominently entrapped as an isolated molecule at low coverage whereas at high loading the filling is primarily pairwise. In M’(28)FAU zeolites with site II partial occupancy (M’ = Mg2+, Ca2+), the distribution of positions occupied by M(CO)(6) is located in the vicinity of the windows in two slightly different sorption sites.