Hydrogen, being a regenerative and environmentally harmless fuel, can play a crucial role in the energetic scenario of the near future. In recent years several systems for solid-state hydrogen storage have been investigated, among which a few metals and metal alloys show the most promising properties. Mg and Mg-based micro and nanocomposites are widely studied for this application owing to the high gravimetric storage capacity, even if a proper microstructure, mainly at the material surface, has to be setup in order to overtake kinetic constraints often related to the high surface reactivity. In this paper, we present our approach to this problem and report the main findings. We have examined the influence on hydrogenation/dehydrogenation characteristics of different modifications of the bulk and surface microstructure of MgH2 powders processed by ball milling, which appears to be one the most useful methods for preparing powders suitable for hydrogen storage.