The present paper analyzes the CO2 emissions from mobile communications and portable wireless electronic devices in the Korea environment. The quantitative and qualitative contributions to CO2 emission reduction of the substitution of renewable energy for traditional electricity as the power supply in these devices are also investigated. Firstly, the national CO2 emission coefficient is temporarily estimated as 0.504tCO2/MWh, which can be regarded as the basis for calculating CO2 emissions in mobile devices. The total annual CO2 emissions from mobile devices is calculated as approximately 1.4 milliontons, comprising 0.3 milliontCO2 for portable wireless electronic devices and 1.1 milliontCO2 for electric equipment required for mobile communication service. If renewable energy sources are substituted for traditional electricity sources in the supply for mobile devices, solar cell and wind turbine systems can reduce CO2 emissions by about 87% and 97%, respectively. However, the use of fuel cell systems will only slightly reduce the CO2 emissions. However, the use of the direct methanol fuel cell system can release 8% more CO2 emissions than that emitted by using traditional electricity sources.