Ni-7(C4H4O4)(4)(OH)(6)(H2O)(3)(.)7H(2)O, a new layered nickel(II) succinate, was prepared hydrothermally (180degreesC, 48 h, autogenous pressure) from a 1:1.5:4.1:120 mixture of nickel (II) chloride hexahydrate, succinic acid, potassium hydroxide and water. It crystallizes in the monoclinic system (space group P2(1)/c, Z = 4) with the following parameters a = 7.8597(1) Angstrom, b = 18.8154(3) Angstrom, c = 23.4377(4) Angstrom, beta= 92.0288(9)degrees, and V= 3463.9(2) Angstrom(3). Its structure, which contains 55 non-hydrogen atoms, was solved ab initio from synchrotron powder diffraction data. It can be described from hybrid organic-inorganic layers, constructed from nickel oxide corrugated chains. These chains are built up from NiO6 hexameric units connected via a seventh octahedron. Half of the succinates decorate the chains, and the others connect them to form the layers. The three dimensional arrangement is ensured by hydrogen bonds directly between two adjacent layers and via free water molecules.