Regions of high excitation gas were detected around various active galactic nuclei. Their shape resembles a cone whose axis is oriented close to the radio axis. The radiation emitted by the nucleus may be responsible for the high ionization of the line emitting gas. Moreover there is evidence that the radiation field should be anisotropic and collimated in a direction close to the cone axis. The authors consider the possibility that a geometrically thick accretion disk is the source of the ionizing continuum and we compare theoretical predictions with observational data. Furthermore they analyze the energetics requirements and the spatial distribution of the extended emitting gas for Seyfert and radio galaxies.