In this talk I will assume that the diphoton excess recently announced by ATLAS and CMS is due to the production of a new resonance and I will focus on three aspects: the estimate of the signal cross section, the information on the total width of the new particle and the possibility of producing it by gamma-gamma collisions. These three topics have been widely discussed in the literature, but with several contradicting statements. By going thorough a critical review of the ATLAS and CMS notes where the excess has been announced, I will try to reconcile these contradictions and give an overview of the main sources of the discrepancies.
