Phosphine oxide complexes of lanthanide metal have been studied to elucidate the fundamental aspects\ud of their structural chemistry and to develop important technological applications mainly in the reprocessing\ud of nuclear fuels and in photoluminescent devices but also in other fields such as gas sorption\ud and homogeneous catalysis. The aim of this review is to give an overview of the range of complexes with\ud phosphine oxides and trivalent lanthanide and yttrium ions, their structural features and applications.\ud �