The synthesis and characterization of five new diethylenetriaminepentaacetic acid (dtpa) ligands, (dtpa)‐N,N″‐bis(alkoxyphenylamide), and their complexation with GaIII, InIII and LuIII are reported. The procedures for the synthesis of all complexes in aqueous media are described as well as a synthetic pathway for the preparation of GaIII complexes in chloroform. All substances were characterized by NMR spectroscopy, mass spectrometry, elemental analysis and HPLC. Single‐crystal structure analysis was performed where applicable, which revealed the presence of hepta‐ and octa‐coordinated isomers for InIII complexes and a nine‐fold coordination of LuIII ions in the solid state. Additional NMR experiments suggested a hepta‐coordinated InIII species in solution, whereas the GaIII complexes appear to be hexa‐coordinated and the LuIII complexes to be octa‐coordinated. Both NMR and HPLC studies indicated the presence of a single isomer in every complex.