Crystals of Na₂[(UO₂)W₂O₈] and α- and β-modifications of Ag₂[(UO₂)W₂O₈] were synthesized by high-temperature solid-state reactions and their structures have been determined. The structure of Na₂[(UO₂)W₂O₈] (triclinic, P1, a = 6.6484(6), b = 7.5308(7), c = 8.4869(7) Å, α = 89.952(2), β = 86.190(2), γ = 73.299(2)°, V = 406.02(6) ų, Z = 2) was solved by direct methods and refined to R₁ = 0.043 (wR₂ = 0.084). The structure of α-Ag₂[(UO₂)W₂O₈] (monoclinic, P2₁/c, a = 8.4263(7), b = 7.4897(7), c = 12.927(1) Å, β = 95.443(2)24°, V = 812.2(1) ų, Z = 4) was solved by direct methods and refined to R₁ = 0.049 (wR₂ = 0.104). The structure of β-Ag₂[(UO₂)W₂O₈] (orthorhombic, Pnma, a = 8.6415(6), b = 7.5610(6), c = 12.4513(9) Å, V = 813.6(1) ų, Z = 4) was solved by direct methods and refined to R₁ = 0.059 (wR₂ = 0.154). The crystal structures of the compounds are based upon sheets of UrO₅ pentagonal bipyramids (Ur = UO₂²⁺, uranyl ion) and WO₆ octahedra with the composition [(UO₂)W₂O₈]. The UrO₅ pentagonal bipyramids share equatorial edges, resulting in chains one polyhedron wide that extend along [010] in all three structures. The WO₆ octahedra share corners to form chains of composition [WO₅] parallel to [010]. Two adjacent [WO₅] chains are linked into double [W₂O₈] chains by the sharing of edges between WO₆ octahedra. The chains of UrO₅ bipyramids and the [W₂O₈] chains are linked into sheets by the sharing of edges between UrO₅ bipyramids and WO₆ octahedra. The sheets are parallel to (100) in Na₂[(UO₂)W₂O₈] and to (001) in α- and β-Ag₂[(UO₂)W₂O₈]. Na and Ag are located in the interlayers, and provide linkage of the sheets. Geometrical parameters of the [(UO₂)W₂O₈] sheets in the structures of Na₂[(UO₂)W₂O₈] and α- and β-Ag₂[(UO₂)W₂O₈] are identical within ∼ 3%, which indicates a relatively rigid sheet. Thus, the role of the interlayer cations is to compensate the charge of the sheet and to link adjacent sheets. The α- and β- modifications of Ag₂[(UO₂)W₂O₈] differ only in stacking sequences of uranyl tungstate sheets and can be considered as Ag₂[(UO₂)W₂O₈]-2M and Ag₂[(UO₂)W₂O₈]-2O polytypes, respectively.