2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/694The main characteristics of the average spectrum of radio quiet AGN in the UV and X-ray range are reviewed, and the emission mechanisms are discussed in the framework of accretion disk models, in particular the ``irradiated cold relativistic disk". It is shown that some problems arise in confronting the predictions of the model to the observations. We propose an alternative model in terms of a hot disk surrounded by a cold Compton thick medium. Finally we mention problems with remote regions of the accretion disk.18 pages, 2 figures, to appear in proc. "AGN in their Cosmic Environment", Eds. B. Rocca-Volmerange & H. Sol, EDPS Conf. Series in Astron. & AstrophysicsAstrophysicstext