The effect of hydrogenation on the magnetic properties and crystal structure of 4f and 5f intermetallics was studied on HoNiAlH_2.0, UNiAlH_2.3 and UNiAlD_2.1. The incorporation of hydrogen into HoNiAl leads to a decrease of the magnetic ordering temperature from 13 to 6 K, while it increases from 19 K to values in the range 90-100 K in the UNiAl-H system. The crystal lattices of all compounds are anisotropically expanded. Moreover, the crystal symmetry is lowered to orthorhombic in HoNiAlH_2.0, but remains hexagonal for UNiAlH(D)_x. Three different deuterium positions were found for both compounds.