Annular diffuser has very strong industrial significance. The existence of hub can guide the flow axially and radially outward. In this paper temperature distribution is numerically investigated in an annular diffuser fitted with two different hub geometries that include twisted rectangular hub and pimpled hub. These two hub shapes are studied and compared as swirl generators. Inlet boundary conditions and annular diffuser geometries for both hub configurations are kept constant with Reynolds number (Re = 4.2 x 104). The results indicate that using both twisted rectangular hub and pimpled hub will impose the flow to follow in a swirl motion and force the temperature to distribute in a helical direction. Temperature distribution will be enhanced as a result of increasing of swirl motion, however the results pointed out that pimpled hub inserts provide better distribution effect.