The study of composite membranes with top layers of different thickness is essentially a method of integral layer scanning. Two-layer composite membranes were formed by coating polymer solution on porous support. Poly(phenylene oxide) (PPO) of different molecular weight and sulfonated PPO were used as top layer polymers. Gas transport properties were examined by gas chromatography and used for calculation of resistance and specific resistance of gas flow through a composite membrane. According to the resistance, the top layers of composite membranes are very inhomogeneous through their thickness. The results were explained by deformation-orientational order which appears during the formation of thin films on a porous support. The interaction between the polymer chains of top layer and the surface of support determines multizone structure of the top layer.