2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/13659Models of black hole accretion disks are reviewed, with an emphasis on the theory of hard X-ray production. The following models are considered: i) standard, ii) super-critical, iii) two-temperature, and iv) disk+corona. New developments have recently been made in hydrodynamical models of accretion and in phenomenological radiative models fitting the observed X-ray spectra. Attempts to unify the two approaches are only partly successful.20 pages. Invited review at the workshop ``High Energy Processes in Accreting Black Holes'', eds. J. Poutanen & R. Svensson, ASP Conf. Series, in pressAstrophysicstext