A comparative study of four series of pyrrhotite-type chalcogenide compounds Fe7-yMyX8 (X = S, Se) with substitution of Ti or Co for iron has been performed by means of x-ray and neutron powder diffraction, and by magnetization measurements. In Fe7-yMyX8 compounds having a ferrimagnetic order at [Formula: see text], the substitution of either Ti or Co for iron is observed to result in a monotonous decrease of the magnetic ordering temperature, while the resultant magnetization shows a non-monotonous behavior with a minimum around [Formula: see text]-1.5 in all the Fe7-yMyX8 families except Fe7-yCoySe8. Suppression of a magnetically ordered state with substitutions in Fe7-yMyX8 is ascribed to nearly zero values of Ti and Co magnetic moments, while the non-monotonous changes of the resultant magnetization are explained by the compensation of the sublattice magnetizations due to the non-random substitutions in alternating metallic layers. The difference in the cation partitioning observed in Fe7-yTiyX8 and Fe7-yCoyX8 is attributed to the difference in the spatial extension of Ti and Co 3d orbitals. High coercive field values (20-24 kOe) observed at low temperatures in the Ti-containing compounds Fe7-yTiyX8 with y ⩾ 3 are suggested to result from the enhancement of Fe orbital moment due to the Ti for Fe substitution.