Hydrogenation was found to be a strong tool for modification of magnetic propertiesand crystal structure of the RE NiAl intermetallic compounds. Non-uniform expansion ofthe unit cell due to incorporation of hydrogen leads to an orthorhombic distortion of the originalZrNiAl-type hexagonal structure. Hydrogenation also largely suppresses magnetic order in allstudied compounds: it weakens exchange interactions, lowers ordering temperatures and modifiesmagnetic 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 maineffect of hydrogenation is not of geometrical character but due to the variation of electronicdensity.