High energy ball milling and subsequent high-pressure torsion method was carried out on nanocrystalline Mg powders catalyzed by 5 wt.% Nb₂O5 and 5 wt.% carbon nanotubes. In the present research two distinct milling routes were performed in order to reveal the influence of the processing conditions on the hydrogenation behavior of the investigated alloys. The hydrogen sorption behavior of the milled powders and the bulk disks was examined in a Sieverts'-type apparatus. Structural characterization of the catalyzed Mg powders and disks has been carried out by high-resolution transmission electron microscopy and X-ray diffraction.