To understand the influence of various crystallographic phases on hydrogen storage properties, ball milling of MgH2 with hexagonal (alpha) and cubic (beta) SiC have been performed. Structural characterization of all samples has been done by X-ray diffraction (XRD) analysis, particle size analysis and scanning electron microscopy (SEM). Investigation of hydrogen desorption properties of prepared nanocomposites has been done using temperature programmed desorption (TPD) technique. Despite the results of structural and morphological characterization of obtained nanocomposites are very similar, TPD spectra show significant differences regarding existence of intermediate temperature peak. In the sample milled with hexagonal SiC this peak originates both from H-2 and H2O, while in the sample milled with cubic phase it only comes from H2O. Both samples exhibit low temperature H-2 peak at 385 K. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.