A series of new layered coordination polymers consisting of Ln[Ph2P(O)-CH2CH2-P(O)Ph-2](1.5) monomeric units, where Ln = Pr(NO3)3, Nd(NO3)(3), NdCl3, Sm(NO3)(3), GdCl3, Dy(NO3)(3), were synthesized and structurally characterized. The majority of prepared compounds display approximately rectangular building blocks. However, the adopted architecture strongly depends on additional nonbridging ligands in the coordination sphere of the cation, as well as on the reaction conditions and the employed solvent. Accordingly, the solvothermally prepared polymers exhibit either parquet-floor or brick-wall architecture, whereas the polymers from gel-diffusion reactions resemble honeycomb networks. The solvothermal reaction of the smallest lanthanide cation Lu3+ with Ph2P(O)-CH2CH2-P(O)Ph-2 led to a molecular compound instead of a polymer.