In this paper the Hole Quasichemical Group-Contribution model (HM) is used to describe phase diagram peculiarities of multicomponent aqueous systems containing hydrocarbons and alcohols. The model correctly describes liquid-liquid (LL), liquid-liquid-vapour (LLV), liquid-vapour (LV) and vapour-vapour equilibria (VVE), and critical and azeotrope curves, The potential use of the HM in the prediction of the solubilities of hydrocarbons in near-critical water and the densities of coexisting phases in the critical region of the system n-hexane-water are presented.