The effect of diluents upon distribution constants of 8-hydroxyquinoline and its 2- and 4-methyl derivatives in two-phase liquid systems has been analyzed using the Kamlet and Taft model. These constants for 5-methyl-8-hydroxyquinoline and 7-(4 ,5 ,7 ,7 -tetramethyl-1 -octenyl)-8-hydroxyquinoline in the chloroform-water system have been also considered.The derived correlations are statistically valid and can be useful for: (1) prediction of distribution constants of 8-hydroxyquinoline and its derivatives in the extraction systems; (2) discussion of solute-solvent interactions in the organic phase; (3) prediction of the distribution constants of appropriate copper(II) complexes.