||The solubility of carbon dioxide (CO2) was investigated using three different 1-butyl-3-ethylimidazolium ([BEIM]) cation based ionic liquids: 1-butyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide ([BEIM][Tf2N]), 1-butyl-3-ethylimidazolium tetrafluoroborate ([BEIM][BF4]), 1-butyl-3-ethylimidazolium hexafluorophosphate ([BEIM][PF6]). The CO2 solubility data in the three ionic liquids was produced by measuring the bubble point and cloud point pressures of the CO2 + ionic liquid mixtures. The temperature range was from 303.15 to 373.15 K. The solubility is determined by CO2 mole fraction in ionic liquids, and the order of magnitude of the CO2 solubility was found to be [BEIM][Tf2N] > [BEIM][BF4] > [BEIM][PF6]. For the correlation and calculation of the experimental data, modified Lydersen-Joback-Reid method was proposed to estimate critical properties and acentric factors of ionic liquids. Conventional van der Waals one fluid mixing rule and Peng Robinson equation of state (PR-EoS) was used to correlate equilibrium pressure acquired from the experiment.