A numerical study of conjugated heat (natural convection-thermal radiation) and mass transfer in a square cavity filled with a mixture of Air-CO2 is presented. The study was performed through laminar and turbulent regimes (10(4) <= Ra <= 10(10)). The cavity is differentially heated with two isothermal walls and two adiabatic. The hot wall is kept at a constant temperature of 75 degrees C with a CO2 concentration of 3000 ppm, whereas the cold wall is considered to be an isothermal wall at 25 degrees C with a CO2 concentration of 500 ppm. Governing equations of mass, energy and concentration were solved by the finite volume method, and a k-epsilon turbulence model was used for the treatment of high Rayleigh numbers. From the results, it was found that in general, convection and total heat transfer amount increases considerably as the mass transfer is taking into account, but it decreases as the Rayleigh number increases. Similarly, it was observed that the radiative heat transfer decreases the heat transfer by convection but increases the total heat transfer inside the cavity, especially for high Rayleigh numbers. (C) 2013 Elsevier Ltd. All rights reserved.