Gas separation membranes composed of sulfonated poly(phenylene oxide) as a support and polypyrrole were prepared by two alternative ways: (1) the support films were saturated by oxidant and then treated with pyrrole vapors (2) the support films were saturated with pyrrole vapor and then treated with the oxidant. Study of the polymerization conditions has shown that the second method of membrane preparation results in formation of a dense polypyrrole layer on the support surface. The membranes were characterized by Fourier transform infrared spectroscopy, ultraviolet spectroscopy, optical microscopy and atomic force microscopy. Measurements of gas transport properties demonstrated that the O-2 vs. N-2 selectivity coefficient of this polypyrrole layer was 15, which is one of the highest values described in the literature.