This study explores the use of COSMO-RS model and Peng-Robinson (PR) equation of state (EoS) to predict the solubility of carbon dioxide (CO2) in specific ionic liquids (ILs). COSMO-RS was employed to estimate of CO2 solubility at atmospheric pressure in eight imidazolium-based ILs resulting from the combination of ethyl, butyl, hexyl, and octyl-imidazolium cations with two anions: bis(trifluoromethylsulfonyl)imide ([Tf2N]) and Trifluoromethanesulfonate ([TFO]). The results indicated relatively acceptable qualitative consistency between the experimental and predicted values. The PR EoS was employed at high pressure by tuning the interaction parameters to fit the experimental data reported in the literature. The model demonstrated excellent accuracy in predicting the solubility of CO2 at pressure values less than the critical pressure of CO2; however, at higher pressures, the calculated solubility diverged from the experimental values. Furthermore, the type of anion and cation used in the IL affected the performance of the PR EoS.