The low‐temperature magnetic ordering of the nonstoichiometric compounds GdD2+x and SmD2+x for ‖x‖neutron diffraction and magnetic susceptibility measurements. It is shown, that both the antiferromagnetic structure and the Néel temperature TN depend strongly on the D concentration. Both for GdD1.93 and for SmD1.85, the magnetic structure is found to be of the type MnO. For higher concentrations, the structure becomes incommensurate with the lattice. For GdD2.00, a helical structure with axis along the 〈111〉 direction is observed. The angle between the moments in the successive (111) layers is found to be 163.8°. For GdD1.93 and GdD2.00, TN values of 20 K and 15.5 K, respectively, are obtained. For SmD2+x, TN is found to be reduced from 9.6 K for x = 0.15 to 8.0 K for x = 0 and to less than 4.5 K for x = 0.15.