The single crystals of ZnCr2Se4 spinel doped with manganese were prepared by the chemical vapour transport in closed silica tubes using stoichiometric contents of ZnSe, MnSe and CrCl3 as the transporting agent. Chemical composition of four single crystals of Zn-Mn-Cr-Se system with different concentration of manganese was analyzed and confirmed by X-ray diffraction study. The structure refinements, taking into account site occupancy factors, indicated that Mn ion shared tetrahedral sites with Zn ion. Thus, the formula describing cation distribution in the system is: Zn1-xMnxCr2Se4. For all x values equal to 0.12, 0.13, 0.18 and 0.24, the observed symmetry was cubic, space group Fd 3m .