Hydrogenation was found to be a strong tool for modification of magnetic properties and crystal structure of the RENiAl intermetallic compounds. Non-uniform expansion of the unit cell due to incorporation of hydrogen leads to an orthorhombic distortion of the original ZrNiAl-type hexagonal structure. Hydrogenation also largely suppresses magnetic order in all studied compounds: it weakens exchange interactions, lowers ordering temperatures and modifies magnetic phase diagrams. A series of hydrides with lower H concentration was studied, as well, and non-continuous variation of their properties with reducing H content indicates that the main effect of hydrogenation is not of geometrical character but due to the Variation of electronic density.