The self-diffusion of water and ethanol for crosslinked and uncrosslinked chitosan membranes have been investigated by pulsed-field gradient nuclear magnetic resonance (NMR) spectroscopy. It has been shown that during diffusion processes, water and ethanol are localized in different parts of the chitosan membrane, In the crosslinked membrane, the self-diffusion coefficient for water is higher, but that for ethanol is essentially lower, than those for the uncrosslinked membrane. For this reason, the mobility selectivity is essentially higher in crosslinked membrane as compared to the uncrosslinked. The sorption selectivity are the same for these two types of membranes.