Single crystals of Pb ₃O ₂(SeO ₃) have been prepared hydro thermally at 230°C. The structure (orthorhombic, Cmc2 ₁, a = 10.529(2), b = 10.722(2), c = 5.7527(12) Å, V = 649.5(2) Å ³) has been solved by direct methods and refined to R ₁ = 0.059 on the basis of 615 unique observed reflections (|F _o| = 4σ _F). The structure is based upon double [O ₂Pb ₃] ²⁺ chains of edge-sharing [OPb ₄] ⁶⁺ tetrahedra. These [O ₂Pb ₃] ²⁺ chains run parallel to [001], and their planes are parallel to (010). The pyramidal (SeO ₃) ² anions are located between the chains; their triangular oxygen atom bases lie parallel to (001) and all (SeO ₃) ^2- groups are pointing in the same direction. A short compilation of [O ₂M ₃] chains of oxocentred M ₄ tetrahedra in minerals and inorganic compounds is provided.