  We used high quality BeppoSAX data of 6 Seyfert galaxies to test realistic
thermal Comptonization models. Our main effort was to adopt a Comptonization
model taking into account the anisotropy of the soft photon field. The best fit
parameter values of the temperature and optical depth of the corona and of the
reflection normalization obtained fitting this class of models to the data are
substantially different from those derived fitting the same data with the power
law + cut--off model commonly used. The two models also provide different
trends and correlation between the physical parameters, which has major
consequences for the physical interpretation of the data
