  Narrow Line Seyfert 1 galaxies (NLS1) are generally believed to host
"under-massive" black holes with respect to the predictions from the host
galaxy -- black hole mass scale relations. Black hole masses in NLS1 are
estimated from the continuum luminosity and the width of broad emission lines.
Here we show that the "mass deficit" can be canceled out if we assume that the
broad line region (BLR) in type-1 AGN has a flat geometry, which is seen
face-on in NLS1. The detection of relativistic jets aligned along the line of
sight in a number of NLS1 supports this picture. Moreover, a flat geometry of
the BLR is also suggested by a general trend of the mass deficit as a function
of the line width observed in other type-1 AGN, from quasars to BL Lac objects,
and is consistent with a simple extension of the Unified Model of AGN to the
BLR geometry.
