The semiconducting compound Cu2SnSe3 has been investigated by means of X-ray powder diffraction and its structure has been refined by the Rietveld method. The compound crystallizes in the monoclinic space group Cc (C-s(4), No. 9), Z = 4, with unit cell parameters a = 6.9670(3) Angstrom, b = 12.0493(7) Angstrom, c = 6.9453(3) Angstrom, beta = 109.19(1)degrees, and V = 550.6(5) Angstrom(3). The refinement of 36 instrumental and structural parameters converged to R-p, = 6.1%, R-wp = 8.6%, R-exp = 5.7%, R-B = 6.4%, S = 1.5, for 4501 step intensities and 280 independent reflections. The structure of Cu2SnSe3 can be described as an adamantane compound derivative of the sphalerite structure. (C) 2003 Elsevier Ltd. All rights reserved.