The compounds Cs2AlP3O10 and Cs2GaP3O10 have been synthesized by solid state reactions and structurally characterised by single crystal X-ray diffraction. They are two dimensional compounds possessing corrugated [MP3O10]2- anionic layers interleaved with Cs+ ions. The layers are built from MO6 octahedra and bent triphosphate groups. Solid state NMR studies corroborate the presence of crystallographically distinct phosphorus atoms of triphosphate groups. © The Royal Society of Chemistry 2000.