Using a weighted sum of gray gases model with gray gas regrouping technique (WSGGM-RG), problems of radiative transfer within three-dimensional enclosures filled with non-homogeneous and non-isothermal combustion gas mixtures were solved. The radiative transfer equation was solved based on discrete ordinate method (DOM) and raytracing method (RTM) with WSGGM-RG. The results using WSGGM-RG were compared with those using the statistical narrow band (SNB) model. The average radiative intensities and radiative heat fluxes using WSGGM-RG corresponded relatively well to those using the SNB model as reference data. A very good computational efficiency was also noted.