Since carbon dioxide, CO2, was revealed as a major greenhouse gas, techniques for its separation, capture, and storage have received increasing interest in recent years. Aqueous amines are the most widely accepted CO2 absorbents, but they cause the problems such as high regeneration energy, thermal degradation, and loss of absorbents due to their volatility. Ionic liquids having high thermal stability, extremely low vapor pressure, and capability of selectively absorbing specific gases have been proposed as new CO2 capturing solvents which may potentially replace aqueous amines. By reviewing the ionic liquids having capability to absorb CO2 reported in previous papers, we seek to develop a comprehensive understanding on the factors that influence the CO2 solubility in ionic liquids such as their structures, absorption temperature, pressure, water content, etc., and to estimate the potential of ionic liquids as CO2 separating media.