From extraction experiments and γ-activity measurements, the extraction constants corresponding to the general equilibrium $$ {\text{Eu}}^{ 3+ } \left( {\text{aq}} \right) + 3 {\text{A}}^{- } \left( {\text{aq}} \right) + {\text{L}}\left( {\text{nb}}\right) \Leftrightarrow {\text{{\text{Eu}}}}{\text{L}}^{ 3+ }\left( {\text{nb}} \right) + 3 {\text{A}}^{ - } \left( {\text{nb}}\right) $$ taking place in the two-phase water–nitrobenzene system ( $$ {\text{A}}^{ - } = {\text{CF}}_{3} {\text{SO}}_{3}^{ - } $$ ; L = macrocyclic lactam receptors denoted by 1, 2, 3 and 4—see Scheme 1; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the EuL3+ complexes in nitrobenzene saturated with were calculated; they were found to increase in the series of 1 < 3 < 4 < 2.