Materials based on II-VI semiconductor compounds in which a fraction of the nonmagnetic cations (e.g. Zn2+) has been randomly replaced by transient metal (TM) ions, are widely known as diluted magnetic semiconductors (DMS). DMS, which display both semiconducting and ferromagnetic properties, have attracted considerable research interest as the new functional device materials, because of their possible application in the spintronics. However, for practical applications, it is important, in particular, to study the mechanisms involved in the magnetic coupling and how they are dependent on the ion spacing and concentration in the semiconducting host. It was considered that Cr-based DMS should reveal an intermediate magnetic behaviour between Brillouin-type paramagnetism, resulting from the single multiplet ground state of the doping ion (e.g. Mn or Co), and Van Vleck-type paramagnetism, due to the singlet ground state of the TM (e.g. Fe). In this report the influence of the Cr impurity concentration on the magnetization of ZnSe is analysed. Chromium-doped ZnSe samples with Cr concentrations varied within 0.00 - 0.30 at. % range were grown by the chemical vapor transport method using iodine as a transport agent. The doping was performed during the growth process. Doping with chromium leads to significant decrease of the magnetization values and to inversion of the magnetization sign at concentrations of the doping impurity higher than 0.10 at. % Cr (Fig. 1). The negative values of magnetization most probably may be caused by diamagnetic contribution of the zinc selenide crystal lattice. Decrease of paramagnetic contribution from [ISe,VZn] complexes may be caused by decrease of its concentration due to the Cr-doping. Chromium ions incorporate into the zinc sublattice nodes, thus chromium doping significantly reduces number of zinc-vacancy nodes which take part in the formation of paramagnetic centers. At the same time, low chromium concentrations in the source materials (0.03 at. %) decrease the value of magnetic field at which the saturation begins (Fig. 1). This indicates some increase in the concentration of the ferromagnetic centers. The hysteresis loops (Fig. 2) confirm the presence of ferromagnetic centers in the crystals. A model, which assumes formation of Cr-Cr pairs, was proposed to explain the magnetic behaviour of the chromium-doped zinc selenide.