International audienceA light Standard Model Higgs boson, with mass between 114 and ~150 GeV, is favored by precise measurements of electroweak radiative corrections and other theory predictions. One of the most important channels to search for this particle in the above mass region is the decay H-->gamma-gamma. This talk reviews the ATLAS discovery potential of a light Higgs boson in the two photon decay. In addition to the inclusive analysis we consider also the reconstruction of diphoton systems produced in association with jets. The studies are based on a realistic detector simulation of Monte Carlo signal and background events