Single crystals of Cu(HSeO4)2(H2O)6 (1) have been prepared from the 5 ml aqueous solution of uranyl nitrate, copper nitrate and selenium acid. The solution was placed in a steel autoclave with a Teflon capsule and incubated for 5 days at 225 ° C. After cooling the autoclave, a transparent homogeneous solution was poured onto a watch glass and left at room temperature. Compound 1 has a triclinic symmetry, space group P-1, a = 6.1192(11), b = 6.3164(11), c = 8.6982(15) Å, α = 70.911(3), = 84.152(3)o, γ = 73.538(4) o, V = 304.67(9) Å3, Z = 2]. The crystal structure have been solved by the direct methods from X-ray diffraction data and refined by the least-squares techniques to R1 = 0.028 (wR2= 0.074) for 1281 reflections with |Fo| ≥ 4σF.