Single crystals of [CH6N3]2[(UO2)2(SeO4)3] (1) and [CH3NH3]2[(UO2)2(SO4)3] (2) have been prepared by isothermal evaporation from aqueous solutions under room-temperature conditions. The crystal structure of 1 has been solved by direct methods [monoclinic, P2, a = 9.9448(15), b = 9.727(2), c = 10.1508(15) Å, β = 90.213(12)°, V = 981.9(3) Å3, Z = 2] and refined to R1 = 0.0696 (wR2 = 0.1611) for 2511 reflections with |Fo| ≥ 4σF using least square techniques. The crystal structure of 2 has been solved by direct methods [triclinic, P1, a = 8.4784(6), b = 9.7873(8), c = 9.8121(7) Å, α = 90.170(2), β = 95.744(2), γ = 90.136(2) °, V = 810.12(10) Å3, Z = 1] and refined to R1 = 0.0146 (wR2 = 0.0336) for 5378 reflections with |Fo| ≥ 4σF using least square techniques. The structures of 1 and 2 are based upon the [(UO2)2(TO4)3]2– (T = Se, S) two-dimensional uranyl layers formed by linkage of U pentagonal bipyramids and TO4 tetrahedra via common O atoms. The layers consist of two types of 4-membered rings; this topology ha