The adsorption behaviour of physically vapour deposited MgF2, LaF3, CaF2, and LiF films on non-heated substrates has been investigated gravimetrically and spectroscopically. It was also shown that the adsorption behaviour differs between the two growth groups into which the fluorides are divided. The strong adsorption of saturated hydrocarbons in CaF2 and LiF films, measured by Fourier transform infrared spectroscopy after maintaining for two years at atmospheric pressure, can be explained by calculation of the water filling degree of the pores and with the assumption of a pore size distribution of the film pores.