The results of systematic equilibrium, kinetic, and relaxometric investigations carried out on the Mn2+ complexes of open-chain and AAZTA ligands indicate that the [Mn(CDTA)](2-) complex has satisfactorily high kinetic inertness (t(1/2) = 12 h at pH = 7.4), which, in turn, may allow its use as a contrast agent in the field of magnetic resonance imaging (as a replacement for Gd3+-based agents).