Concentration and/or space-dependent diffusional mass transport through a dense membrane were investigated. A quasi-analytical approach is given in order to calculate the concentration distribution in the membrane and the mass transfer rates in the case of a single component as well as of binary component diffusion transport. Both properties can be expressed by closed mathematical expressions independently of the concentration dependency function of the diffusion coefficient. The coupled binary diffusion was described by the Maxwell-Stefan theory. Two examples of mass transport, namely binary pervaporation of water/ethanol as well as binary separation of methane/ethane by a zeolite membrane, were calculated, which demonstrate the simplicity of the model equations.