The effect of solvent and mobile-phase composition on adsorption characteristics in liquid-phase absorption is studied. Comparing experimental adsorption data for several organics in both gas- and liquid-phase systems confirms that adsorption equilibrium constant K and isosteric heat of adsorption Q(st) are smaller than those in corresponding gaseous systems. The logarithm of K almost linearly increases as methanol composition decreases. Solvophobic theory applied quantitatively analyzes these solvent effects. Estimation methods for three parameters influence calculation results : solvent effects on K can be quantitatively analyzed; the adsorbability of adsorbates can be estimated from the value of Delta G(solv) for each homologue in a reversed-phase liquid chromatographic system; and the solvent effect on Q(st) cannot be satisfactorily interpreted. It is, however, confirmed that Q(st) is influenced by a solvent and an apparent small value is observed in liquid-phase adsorption.