Single crystals of (VO)(2)(SeO3)(3) have been prepared from SeO2 and V2O5 The crystal structure has been determined by single-crystal X-ray diffraction. Crystal data : (VO)(2)(SeO3)(3), M-r = 514.75; monoclinic, space group P2(1)/a (No. 14); cell parameters a = 9.151(1) Angstrom, b = 6.353(1) Angstrom, c = 14.992(1)Angstrom, beta = 93.538(5)degrees, and Z = 4. The structure consists of VO6 octahedra and SeO3 groups. The vanadium octahedra either are edge-sharing and form [V2O6.66](3.33-) groups or are corner-linked through an [SeO3/2](+) cation. The structure may be rationalized in terms of connecting layers of {2[SeO2/2O1/3](4/3+)[VO1/1O4/2O1/3](5/3-)}(+) cations and {[SeO3/2](+)[VO1/1O5/2](2-)}(-) anions.