Thermodynamic models of multicomponent adsorption in liquid chromatography are summarized and reviewed. A general description of adsorption equilibrium is presented, which is followed by simplified approaches that can be adopted for practical applications. Synergistic and competitive adsorption effects accompanying chromatographic elution are illustrated and methods of their predictions are indicated. The influence of a mobile phase modifier on the retention behavior of chromatographed species is discussed. A manner of mathematical predictions of competitive adsorption of modifiers and solutes is presented. Also in this case the analysis starts with a thermodynamically grounded general description and ends with simplified models suitable for practical purposes of design and optimization of chromatographic separations.