In ferromagnetic materials hydrogen has been observed to give rise to three types of magnetic relaxations: 1) diffusion aftereffect due to a long-range migration of hydrogen within domain walls, 2) orientation after-effect due to the rearrangement of anisotropic hydrogen-impurity complexes, 3) magnetic cold-work peak resulting from a condensed hydrogen atmosphere in the dislocation cores. These three types of relaxation have been observed in Ni and α-Fe single crystals. In particular we have investigated the orientation after-effect of C-H and C-D complexes in Ni crystals. A considerable isotope effect has been observed which qualitatively is explained by a harmonic-oscillator model. In α-Fe deformed plastically at r.t. a magnetic after-effect at 18 K has been observed which is attributed to the thermally activated formation of double kinks (α-peak) in nonscrew dislocations. After charging with hydrogen this relaxation peak vanishes and a cold-work peak at 130 K appears. A further relaxation peak observed after quenching in a hydrogen atmosphere is supposed to be due to the thermally activated motion of kinks on screw dislocation in the second-order Peierls potential.