Magnesium hydride and selected magnesium-based ternary hydride (Mg 2FeH 6, Mg 2NiH 4, and Mg 2CoH 5) syntheses and modification methods, as well as the properties of the obtained materials, which are modified mostly by mechanical synthesis or milling, are reviewed in this work. The roles of selected additives (oxides, halides, and intermetallics), nanostructurization, polymorphic transformations, and cyclic stability are described. Despite the many years of investigations related to these hydrides and the significant number of different additives used, there are still many unknown factors that affect their hydrogen storage properties, reaction yield, and stability. The described compounds seem to be extremely interesting from a theoretical point of view. However, their practical application still remains debatable.