Gamma Astronomy: open theoretical problems

The recent observations of high energy photons have produced results of extraordinary interest. In this contribution some of these results are reviewed, and the main open problems associated with these observations are discussed. Two main themes are present: the first is the investigation of the existence of photons associated with the annihilation (or decay) of dark matter particles, the second is the production of photons associated with the acceleration of charged particles (p, nuclei and e±) to relativistic energies in different astrophysical sources, and their subsequent propagation.