Solutions of generalised Maxwell-Stefan equations (GMSE) for porous and dense polymer membranes are presented. The solution for porous membranes is validated using multicomponent membrane extraction and for dense membranes - using pervaporation process. The simulation results were verified experimentally. The results reveal that GMSE enable successful simulation of both processes. In the pervaporation process the method predicted properly the mass fluxes even in the case when in the system appeared the reverse diffusion.