In this work PEEK-WC asymmetric membranes were used in the separation of hydrogen mixtures of industrial interest. The membranes were prepared by the wet phase inversion technique using tetrahydrofuran as solvent. The effects of the casting conditions (different non-solvents, temperature of the coagulation bath, casting knife gap sets) on the membrane morphology were analysed and strictly related to the transport properties such as permeance and selectivity. The ideal membrane performance was analysed with pure gases (H-2, N-2, CO2, CH4) and H-2/CH4 and H-2/N-2 mixtures of different compositions at 30-80 degrees C and up to 9 bar of feed pressure. Significant differences were observed between the measured selectivities of pure gas and separation factors of gas in mixture. in gas mixture experiments, no variation of hydrogen flux was observed among the different feeds, whereas the permeance of the less permeating species, i.e., N-2 and CH4, Was significantly higher than that measured with pure gases. However, interesting values of purity of the hydrogen-rich stream recovered in the permeate were obtained, achieving up to 90-95%. (C) 2009 Elsevier B.V. All rights reserved.