The Cd1-xMnxTe (0 ≤ x ≤ 0.55) single crystals were grown by the vertical Bridgmen method. The Vickers microhardness measurements on the grown crystals showed a solid solution hardening effect with two hardness maximums at x ≈ 0.15 and x ≈ 0.40. In this paper we report on investigations concerning possible phase separation, ordering effect and structural distortion. To understand this complicated variation of the microhardness, we carried out electronic band structure calculations (under both normal and strained conditions) using supercell psedopotential method, with a set of particular atomic arrangements. We demonstrate a close correlation between the calculated shear modulus and experimental microhardness. Summarizing the calculations we conclude that the first maximum is connected with distortion phenomena. The second hardness maximum we explain by a non-random distribution of the cations and some nanoclastering of cations which could play the role of "nano" phase separation.