This study aims to use perturbed-chain statistical associating fluid theory (PC-SAFT) to describe the phase behavior of systems containing deep eutectic solvents (DESs) and ionic liquids (ILs). The DESs are based on tetrabutylammonium chloride and tetrabutylammonium bromide as hydrogen bond acceptors, and levulinic acid and diethylene glycol as hydrogen bond donors in the mole ratio of 1:2 and 1:4, respectively. Predictions of phase equilibria by PC-SAFT were compared with the results of COnductor like Screening MOdel for Real Solvents (COSMO-RS) and non-random two-liquid (NRTL). In this work, low viscosity ether-and pyridinium-based ILs [E n Py] [NTf 2 ] and [C m Py][NTf 2 ] were used for vapor-liquid equilibrium systems, while 1-(2-methoxyethyl)-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)-amide and 1-propyl-3-methylimidazolium bis{trifluoromethylsulfonyl}imide with n-heptane + thiophene and n-hexane + ethylbenzene were used in the liquid-liquid extraction, respectively. In the last part, the phase behavior of the mixtures of perfluoroalkylalkanes with their linear alkane counterparts was studied and compared with the SAFT-Mie pair potential.