The linear free energy relationship (LFER) analysis based on the Hammett equation has been applied for dissociation processes of 8-hydroxyquinoline and its derivatives in aqueous and 1,4-dioxane-water solutions. The effects of temperature, composition, and ionic strength of the solutions have been discussed. The derived semiempirical correlations are of high statistical quality and of good predictive power which permit the reliable evaluation of dissociation constants 8-hydroxyquinoline and its derivatives under specified experimental conditions: (i) temperature from (289 to 333) K, (ii) mol fraction of 1,4-dioxane ranging from (0 to 0.380), and (iii) ionic strength of solution changing from 0 to 5 mol.dm(-3).