AbstractThe X‐ray excited emission spectra of gadolinium acetate tetrahydrate, [Gd ⊂ 2.2.1]Cl3·2H2O and Gd[C3F7COCHCOC(CH3)3]3 (or Gd[FOD3), are reported. The first two compounds show strong Gd3+ emission (6P←8S) at room temperature, while the third compound gives rise to strong ligand emission, but only at very low temperature. Eu(FOD)3, however, shows intense Eu3+ emission upon X‐ray excitation. The Gd3+ emission spectra show many vibronic lines and, although their intensity is weak, it is much higher than generally accepted. These vibronic lines indicate which groups coordinate the Gd3+ ion and it is shown that their intensity increase as the ligand polarizability increases.