Mg thin films with various thicknesses ranging from 50 to 1000 nm capped with Pd have been prepared by thermal evaporation and their hydrogen sorption properties were examined following the electrical resistance change. The study showed that the hydrogenation and dehydrogenation temperatures correlate with the film thickness, thinner films reacting with hydrogen at reduced temperatures. It is concluded that films thinner than 200 nm react fully with hydrogen, while a considerable portion of the thicker films remain unreacted. The significance of this is discussed with reference to the design of hydrogen storage systems based on thin films or nanoparticles. (C) 2013 Elsevier B.V. All rights reserved.