CO2 as a refrigerant for commercial refrigeration systems in Europe has been gaining increasing customer acceptance and market penetration since being introduced on the market almost a decade ago. The high efficiency of CO2 in commercial refrigeration systems at lower ambient conditions coupled with the relatively low number of hours these systems operate at high ambient conditions in mid to northern Europe have made these systems attractive from an energy efficiency perspective. The very low Global Warming Potential (GWP) of CO2 when compared with typical refrigerants used in these systems coupled with the relatively high leakage rates for typical commercial refrigeration systems have made CO2 very attractive from an environmental perspective. Data is showing that the performance of these systems is increasing year over year as more attention is paid to system design, commissioning, and maintenance. In order for these systems to become competitive globally, the energy efficiency of these systems must become competitive with incumbent refrigerants in higher ambient conditions. There are a number of technology options at various stages of maturity which show a path to achieving this goal.