Based on the PC-SAFT equation of state, a group-contribution method is developed for the determination of binary interaction parameters (k(ij)) between polymers and solvents (GCM-k(ij)). Applying simple geometric combination rules, the k(ij) values can be calculated from binary interaction parameters between polymer groups and solvent groups (k(ps)). 80 different k(ps) values allow the calculation of a k(ij) for polymer/solvent systems with polymers consisting of -CH3, > CH2, > CH2,HDPE, >(CH)-, > C <, > CHAr, > C-(Ar) and -(C=O)-O-groups and solvents containing CH3, > CH2, >(CH)-, > CH2,Cyclo, >(CH)-(Cyclo), =CH2,alkene, =(CH)-(alkene), > CHAr, > C-(Ar), -O-, > C=O and -(C=O)-O-groups. Using earlier-published group-contributions for polymer parameters (Peters etal. 12,3]) in combination with the proposed GCM-k(ij) for polymer/solvent systems allows for predicting liquid-liquid phase equilibria, vapor-liquid phase equilibria and excess enthalpies of binary polymer/solvent and copolymer/solvent as well as ternary polymer/solvent 1/solvent 2 systems in good agreement with experimental data. (C) 2013 Elsevier B.V. All rights reserved.