The main characteristics of the average spectrum of radioquiet AGN in the UV and X-ray range are reviewed, and the emissionmechanisms are discussed in the framework of accretion disk models,in particular the "irradiated cold relativistic disk". It is shown thatsome problems arise in confronting the predictions of the model to theobservations. We propose an alternative model in terms of a hot disksurrounded by a cold Compton thick medium. Finally we mentionproblems with remote regions of the accretion disk.