Polymer/metal nanocomposites films with different morphologies have been prepared from polyetherimide and palladium acetate with Pd amount ranging from 0 to 15 wt%. In a first step, hybrid precursor films have been obtained from polymer/metal complex solutions and the metal nanoparticles have been then generated within the PEI matrix by annealing the precursor film under different conditions. The membrane nanostructuration process and the final membrane morphology have been discussed as a function of the metal precursor amount and annealing conditions. The gas transport properties of the membranes have been analysed for CO(2), He and H(2). Specific interactions between hydrogen and the Pd based nanoparticles have been evidenced and the gas transport mechanisms have been discussed as a function of the gas nature, the nanoparticles structure and the nanoparticles location within the membrane. (C) 2010 Elsevier B.V. All rights reserved.