Cinnamic acid derivatives are natural antioxidants with increasing interest and application trend by the food, pharmaceutical and cosmetics industries, which create a wide research area for the design of physical and chemical processes where these compounds are involved. Solvent selection is a very important design parameter for optimization efficiency of such processes. Ionic liquids constitute a group of solvents that can serve as alternative to the commonly used volatile organic solvents. Solubilities of cinammic acid derivatives in imidazolium based ionic liquids, in organic solvents and in binary solvent mixtures composed of an ionic liquid and an organic solvent have been experimentally determined recently in our laboratory, but their limited number is inadequate for design purposes. The time-consuming experiments combined with the huge number of diverse ionic liquids, make the existence of thermodynamic predictive models of paramount importance. Conductor-like Screening Model for Real Solvents (COSMO-RS) is a unique tool with quantum chemical background that enables solubility predictions and is unrestricted to nature of substances or availability of experimental data. The aim of this work is to evaluate the accuracy of the COSMO-RS model in solubility predictions of cinnamic acid derivatives in ionic liquids, organic solvents and in binary solvents composed of an ionic liquid and an organic solvent. The privileged capability of the model for quantification of the three types of molecular interactions (misfit, hydrogen bonding and van der Waals) along with the corresponding excess enthalpies have been utilized for the analysis of the governing energy interactions that determine solubility. Even though in some cases COSMO-RS predictions show significant deviations from the experimental data, in most cases they are qualitatively consistent with them, indicating that COSMO-RS is a suitable model for a priori solvent screening. Finally, the UNIFAC model has been applied for the case of solubilities in organic solvents just for comparison purposes. (c) 2014 Elsevier B.V. All rights reserved.