  In this work we aim at addressing the still open question about the nature of
Narrow-Line Seyfert 1 (NLS1) galaxies: are they really active nuclei with lower
mass Black-Holes (BHs) than Seyfert 1 (S1) and quasars? Our approach is based
on the recently discovered physical connections between nuclear supermassive
BHs and their hosting spheroids (spiral bulges or ellipticals). In particular
we compare BH masses of NLS1s and S1s analyzing the properties of their hosts
by means of spectroscopic and photometric data in the optical wavelength
domain. We find that NLS1s fill the low BH mass and bulge luminosity values of
the BH mass - bulge magnitude relation, a result strongly suggesting that NLS1s
are active nuclei where less massive BHs are hosted by less massive bulges. The
correlation is good with a relatively small scatter fitting simultaneously
NLS1s, S1s and quasars. On the other hand, NLS1s seem to share the same stellar
velocity dispersion range of S1s in the BH mass - stellar velocity dispersion
relation, indicating that NLS1s have a smaller BH/bulge mass ratio than S1s.
These two conflicting results support in any case the idea that NLS1s could be
young S1s. Finally we do not confirm the significantly non linear BH--bulge
relation claimed by some authors.
