  We present a new, detailed, analysis of the spatial distribution of Galactic
HII regions, exploiting a far richer database than used in previous analyses.
Galactocentric distances have been derived for 550 objects. Distances from the
Sun could be unambiguously derived from velocity data for 117 of them, lying
either outside the solar circle (84) or on a line-of-sight tangential to their
orbit (33). For 177 further sources, distance estimates are made possible by
the use of auxiliary data. A highly significant correlation between luminosity
and linear diameter was found and the corresponding least-square linear
relationship in the log-log plane was used to resolve the distance ambiguity
for an additional 256 sources. Within the solar circle the thickness of the
distribution of HII regions around the Galactic plane was found to be
comparable to that of OB stars (Bronfman et al. 2000). At larger galactocentric
radii the shape of the distribution reflects that of the warp, and its
thickness along the z axis increases with increasing distance from the Galactic
centre. We also confirm, for a much larger sample, the previously reported
positive gradient of electron temperature with galactocentric distance.
