[en] Interaction of hydrated complexes of tris-β-diketonates of yttrium subgroup lanthanides with macrocyclic polyether 18-crown-6 was investigated according to the data of ¹H NMR and NMR relaxation spectroscopy (RS). Formation of complexes with different ligands of 1:1 stoichiometric relation with 17±4M^-1 complexing constants was established. Quantitative analysis of lanthanide-induced shift on ¹H nuclei of formed complexes was used to determine that the last ones were isostructural. Entering of 18-crown-6 molecule into the composition of coordination sphere of lanthanide ion was concluded according to RS NMR data