Carbon dioxide (CO2) is the most important greenhouse gas, causes global warming since industrial era. The developing countries of Asia are now amongst the fastest growing economies in the world and India is the third largest CO2 emitter with 0.44 PgC/yr in 2010, after China and USA. In this reference, a regional air quality model (WRF-CO2) has been set up for South/East Asia and has been run for the years 2010 – 2012, with three major CO2 flux components from terrestrial biosphere, fossil fuel combustion and ocean, to investigate the variations of atmospheric CO2. Apart from the WRF-CO2, output from a global Atmospheric Chemistry Transport Model (ACTM) and observational data from nine observational sites are used. It has been shown that biases in the WRF-CO2 simulations varied widely, depending on representation of surface fluxes and meteorology around the observation site. Analysis of the individual components of CO2 from the WRF-CO2 shows that ocean flux has least contribution to all sites (<10%). Few sites (Mt. Waliguan, Nainital, Cape Rama and Lulin) show dominance of biospheric flux over fossil (>80%). However, two urban sites in Hong Kong show somewhat similar contribution of both the fluxes. Statistical analysis from monthly mean CO2 time series shows, correlation coefficient and normalised standard deviation are generally equal or better for the WRF-CO2 than the ACTM. Overall, seasonal amplitudes and timings of seasonal maximum/minimum are better simulated by the WRF-CO2 than ACTM. Additionally, the WRF-CO2 is able to resolve fine scale structures, particularly in daytime. More results will be discussed in details during presentation.