CNT/Polymer nanocomposites have been fabricated by dispersing (0.1%) weight fraction of SWNT and MWNT in polycarbonate matrix separately using benzene as a solvent. Alignment has been performed by inducing DC electric field (500 V/cm). X-ray diffraction measurements have been performed to confirmation of SWNT, MWNT and their presence in PC matrix. Gas permeability has been found to be increased in aligned CNT/polymer nanocomposites comparison to random dispersed CNT/polymer nanocomposites. The electrical conductivity in aligned CNT/polymer composite membranes indicates two resistive regions. Experimental results exhibits here that CNT/polymer nanocomposite membranes can be used as good hydrogen separating media. Surface morphology of aligned CNT/polymer nanocomposites was confirmed by optical microscopy. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.