Phase equilibria of copolymer–monomer mixtures have been modeled on the basis of experimental cloud-point pressure curves for poly(ethene-co-acrylic acid) and for poly(ethene-co-methacrylic acid). The monomer system was ethene. In case of poly(ethene-co-acrylic acid), in addition, ethene–acrylic acid mixtures were used as the solvent. The association term of the PC-SAFT equation of state has been extended to account for the polydispersity of the copolymer samples. For this purpose, two pseudo-components were introduced for each copolymer. The amount and the molecular weight of these components were related to the number and weight averages of the copolymer material, Mn and Mw, respectively. For the strongly hydrogen-bonded systems, the influence on cloud-point pressures of copolymer composition and of molecular weight distribution can be adequately described by PC-SAFT modeling with temperature-independent parameters.