Abstract A new lead diphosphonate, Pb 2(O 3PCH 2C 6H 4CH 2PO 3) was hydrothermally synthesized from tetraethyl α, α′- p-xylenediphos-phonate and Pb(NO 3) 2. The structure was solved and refined using X-ray powder diffraction data. It crystallizes in the monoclinic space group P2 1/ c, with a = 467.84(2), b = 2007.98(9), c = 639.10(2) pm, β = 101.020(3)°, V = 589.31(4) 10 6 pm, Z=2, w R p=0.034, R p=0.027, R F2=0.061, R F=0.036. The structure is built from corner-linked [PbO 4] polyhedra, containing a lone pair of electrons. These polyhedra are connected to layers by phosphonate groups, RPO 3 2− and through the organic diphosphonic acid to a three-dimensional structure. Thermogravimetric as well as IR spectroscopic studies are also presented.