The change in the magnetic and crystallographic properties was studied in single crystals of hydrides R2Fe14BH3.4 (R = Y, Gd). The absorption of hydrogen leads to an anisotropic expansion of the crystal lattice, a great change of thermal expansion coefficients, increasing of Curie temperature and Fe-ion magnetic moments and weakening of Gd-Fe exchange interaction. The hydrogen significantly reduces the uniaxial anisotropy of Fe-sublattice unlike the plane anisotropy of Gd-sublattice, which results in the appearance of a spin-reorientation phase transition in the hydride with Gd.