We test the disk/corona model of Janiuk et al .
( 2000 ) against the composite mean optical/UV/soft X-ray spectrum of radio loud and radio quiet quasars from Laor et al .
( 26 ) which applies to faint quasars .
The model well represents the optical/UV continuum if the hardening of the locally emitted spectrum is included , with the color to effective temperature ratio f \sim 2 in the inner 20-30 Schwarzschild radii .
Comptonization seen in the soft X-ray band is well explained by the adopted corona model in the case of radio loud objects .
However , this Comptonization is much stronger in radio quiet objects and additional ad hoc assumed Comptonizing medium must be present .
We speculate that perhaps in both types of quasars there is a strong outflow of the hot plasma ; this plasma is collimated in radio loud objects but not collimated in the radio quiet objects so it is present along the line of sight , serving as the required Comptonizing medium .
Hard X-ray power law is not explained by the model and it may come from non-thermal component of electron plasma , as it is the case for galactic black holes in their soft states .