Can Flat Spectrum Radio Quasars make most of the overall gamma--ray background ?

The contribution of discrete sources to the gamma–ray background is modeled. Flat spectrum radio quasars are known to make a substantial contribution to the hard (E > 100 MeV) background. The so called MeV bump", however, cannot be accounted for in terms of known classes of sources even taking into account the newly discovered class of objects with a broad band spectrum sharply peaked in the MeV range (MeV blazars"). Even in the most optimistic case the predicted intensity falls short of at least a factor three.