The phase diagram of the Poly-L-Lactic-Acid (PLLA), dioxane and water system was derived by using the lattice fluid model generalized for specific interactions. A qualitative analysis of Hansen solubility parameters together with empirical observations were adopted to reduce the number of adjustable parameters. The as-selected model parameters were derived by fitting a set of cloud point curves; consequently, the complete phase diagram of the system was computed. The use of specific interactions between species gave out a quantitative agreement with a set of experimental data, whereas changing the polymer polydispersity the agreement is only qualitative. In principle, the presented procedure could be adopted for the calculation of liquid-liquid equilibria in ternary polymer solutions with similar features of PLLA-dioxane-water system. (C) 2011 Elsevier B.V. All rights reserved.