The preparation and characterization of the europium(III) and gadolinium(III) oxydiacetate compounds {[Ln2(oda)3(H₂O)2].5H₂O}n are described. The crystallographic data reveal a novel structural modification within the lanthanide oxydiacetate series. Also, the first species of a lanthanide(III) containing oda and Hoda simultaneously, [Eu(oda)(Hoda)(H₂O)].2H₂O, is reported.