A model for heterogeneous (solid-fluid) photochemical reactors, previously developed and validated experimentally, has been used to investigate the effects produced by absorption and scattering on different variables associated with the reactor performance. With this purpose a parametric study was conducted analyzing the effects engendered by changes in the scattering inert center concentration, scattering center characteristics, and radiation absorbing species concentration on the following properties of the heterogeneous system : (i) spatial and directional distribution of radiation intensities, (ii) local Volumetric rate of energy absorption, (iii) reactor volume averaged rate of reaction for a simple reaction occurring in the fluid phase, and (iv) radiation absorption efficiency inside the reactor. The effect of adopting different models of the scattering phase function for computing the radiative transfer equation was also studied. Operating conditions under which scattering effects may be significant were defined. It was found that there exist combinations of the optical parameters where addition of inert scattering centers may reduce the rate of reaction in as much as 50%.