Quaternary Cu2ZnSnSe4 (CZTSe) is a promising low cost alternative absorber material for thin film solar cells. A record efficiency of 12.6% was reported for a Cu2ZnSn(S,Se)4 (CZTSSe) based thin film solar cell [1]. The polycrystalline CZTSSe absorber layers exhibits an off-stoichiometric composition which causes intrinsic point defects (vacancies, anti-sites, interstitials). These defects determine the electronic properties of the material in a crucial way. This work focuses on the synthesis and characterization of off-stoichiometric CZTSe powder samples. In literature [2] different off-stoichiometric kesterite types have been suggested, so called; A-type: Cu-poor/Zn-rich, Cu2-2xZn1+xSnSe4 (x=0.025-0.125); B-type: Cu-poor/Sn-poor, Cu2- 2yZn1+3ySn1-ySe4 (y=0.025-0.075) and C-type: Cu-rich/Sn-rich, Cu2+2zZn1-3zSn1+zSe4 (z=0.025- 0.075). All powder samples were synthesized by solid state reaction from pure elements in sealed evacuated silica tubes in a one zone furnace. The first reaction took place at a temperature of 750°C with several temperature holding steps (250°C, 450°C, 600°C) in between. After reaction all samples were grinded, pressed in pellets and annealed again in evacuated and sealed silica tubes at 750°C. In the ternary phase diagram Cu2Se-ZnSe-SnSe2 the single phase kesterite region is indicated to be very narrow [3], therefore the formation of secondary phases is highly expected. To determine phase content and chemical composition of the obtained samples, an electron microprobe system equipped with wavelength dispersive X-ray (WDX) analysis was used. The measurements proved the presence of CZTSe as main phase within all the different off-stoichiometric type synthesized samples. The lattice parameters a and c of the CZTSe main phase were determined by Rietveld analysis of XRD data collected using a PANalytical X‟pertPro MPD diffractometer. The Rietveld refinements were performed by FullProf software [4] using the kesterite structure model for the refinement procedure, because stoichiometric CZTSe crystallizes in the kesterite type structure [5]. A correlation between the occurrence of secondary phases and variation of the lattice parameters could be noticed (Figure 1); for instance the c/2a value is lower in samples containing SnSe2 compared with CuSe/Cu2Se containing samples. The samples in which secondary phases were not detected have higher a lattice parameter value. The study of the chemical composition, occurrence of secondary phases and structural properties of 3 different types of offstoichiometric CZTSe samples will be presented.