Ionic liquids (ILs) gained a lot of attention, from both academe and industry, as alternative liquids for different types of applications. Chemical and physical characteristics can be designed with the large availability of cation and anions. Experimental measurement of all these systems is not practically feasible, hence requiring the use of a computational predictive model study. This work evaluates the prediction of the activity coefficient (γs�) at infinite dilution in several classes of ILs using the conductor-like screening model for real solvents (COSMO-RS), a model based on unimolecular quantum chemistry calculations. Comparison of the experimental γs� value with COSMO-RS predicted data is carried out, and absolute average relative deviation was determined to be 24.1, indicating that the COSMO-RS model presents a reliable prediction to determine γs� in a wide range of ILs. The observation also confirms that polarizability of ILs plays a crucial role in their interaction with thiophene. With respect to cation impact, it is more evident to state that γs� decreases with increasing the cation size. The results shown here help in understanding of IL-thiophene interactions. The effect of various structural features of ILs on γs� can be observed, which AIDS in the development of various steps for the design of most suitable ILs with improved interaction with thiophene. © 2016 American Chemical Society.