In this work, gas permeability of composite membranes of Polycarbonate (PC) and Multi walled carbon nanotubes (MWCNTs) with different approaches have been examined. Effect of MWCNTs alignment in PC matrix for gas permeability as well as selectivity was explored. It has been observed that PC membranes having aligned MWCNTs have higher permeability for all gases as compared to randomly oriented MWCNTs. For improving the selectivity further, functionalized MWCNTs with Pd nanoparticles were dispersed in PC and found more selective towards hydrogen than other gases due to absorption of H-2 in Pd nanoparticles. These composite membranes were characterized by Raman spectroscopy, Scanning Electron Microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) for confirmation of functionalization and distribution of MWCNTs in PC matrix. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.