Current research on coordination chemistry is largely aimed at metal-organic frameworks (MOFs). These compounds consist of inorganic centers (transition metal atoms, lanthanides) and organic ligands and have regular one-, two- or three-dimensional structures. Such arrangements may lead to desired properties such as high thermal stability, luminescence (Eu, Tb compounds), porosity or ability to selectively catalyze reactions. Our research if focused on coordination compounds of lanthanides with bidentate and polydentate phosphine oxide ligands. Lanthanides are used as hydrated salts (nitrates and chlorides), and the most frequently used ligands are diphosphine dioxides of a Ph2P(O)-X-P(O)Ph2 general formula in which X = (CH2)n, (C5H4)2Fe, (C6H4)2O, etc. The structures of resulting coordination compounds depend on the lanthanide cation, additional anions in the coordination sphere of the cation, the length of the ligand and its flexibility. Flexible ligands adopt both chelating and bridging coordination modes, while rigid ligands act only as bridging and are more likely to form polymeric structures. We have prepared a number of chelates and 1D and 2D polymers, and discussed the relationships beween reactants and product structures. Therefore, we can now do some structural predictions regarding future syntheses.