Neutron diffraction experiments permitted to locate hydrogen (deuterium) atoms in the compounds Mn//2//3Y//6D//x, x equals 8. 3; 18; 23 whose magnetic behavior is appreciably different from that of the alloy Mn//2//3Y//6. No evidence of a Mn-Mn critical distance corresponding to a Pauli-paramagnetic behavior of the hydride (deuteride) was found.