We report on the analysis of the photometric and spectroscopic properties of a sample of 29 low redshift ( z < 0.6 ) QSOs for which both HST WFPC2 images and ultraviolet HST FOS spectra are available .
For each object we measure the R band absolute magnitude of the host galaxy , the C iv ( 1550 Å ) line width and the 1350 Å continuum luminosity .
From these quantities we can estimate the black hole ( BH ) mass through the M _ { \mathrm { BH } } - L _ { \mathrm { bulge } } relation for inactive galaxies , and from the virial method based on the kinematics of the regions emitting the broad lines .
The comparison of the masses derived from the two methods yields information on the geometry of the gas emitting regions bound to the massive BH .
The cumulative distribution of the line widths is consistent with that produced by matter laying in planes with inclinations uniformly distributed between \sim 10 ^ { \circ } and \sim 50 ^ { \circ } , which corresponds to a geometrical factor f \sim 1.3 .
Our results are compared with those of the literature and discussed within the unified model of AGN .