Mobile air conditioning (MAC) systems of light-duty vehicles consume the most energy among auxiliary parts. Vehicle CO2 reduction policies in Korea, US EPA and European Commission include the strategies for vehicle manufacturers to introduce high-efficient MAC technologies by giving CO2 incentive. One of important parts in the strategies is to set up how to evaluate added CO2 by MAC operation and how to differentiate advanced high-efficient MAC technologies. In this study, to evaluate CO2 emission added by MAC operation, four Korean vehicles were tested on chassis dynamometer with various test modes and different load conditions to MAC system. The driving cycles are CVS-75 used in emission certification and fuel consumption tests in Korea, SC03 used in pollutant emission regulation in driving condition of MAC operation in US, NIER modes used in developing vehicle emission factors in Korea and Euro-MAC under development for evaluating CO2 by MAC in European Union. The test results have shown that the higher efficient MAC technologies add the lower CO2 emission in all test methods. Considerable reduction of vehicle CO2 emission in MAC operation would be expected by introducing high-efficient MAC technologies.