The Perturbed-Chain SAFT (PC-SAFT) equation of state is applied to pure polar substances as well as to vapor-liquid and liquid-liquid equilibria of binary mixtures containing polar low-molecular substances and polar co-polymers. For these components, the polar version of the PC-SAFT model requires four pure-component parameters as well as the functional-group dipole moment. For each binary system, only one temperature-independent binary interaction k(ij) is needed. Simple mixing and combining rules are adopted for mixtures with more than one polar component without using an additional binary interaction parameter. The ability of the model to accurately describe azeotropic and non-azeotropic vapor-liquid equilibria at low and at high pressures, as well as liquid-liquid equilibria is demonstrated for various systems containing polar components. Solvent systems like acetone-alkane mixtures and co-polymer systems like poly(ethylene-co-vinyl acetate)/solvent are discussed. The results for the low-molecular systems also show the predictive capabilities of the extended PC-SAFT model. (C) 2003 Elsevier B.V. All rights reserved.