  The Lockman Hole is well known as the region with the lowest neutral atomic
hydrogen colum density on the entire sky. We present an analysis of the soft
X-ray background radiation towards the Lockman Hole using ROSAT all-sky survey
data. This data is correlated with the Leiden/Dwingeloo survey (Galactic HI
21cm-line emission) in order to model the soft X-ray background by using
radiative transfer calculations for four ROSAT energy bands simultaneously. It
turns out, that an important gas fraction, ranging between 20-50%,of the X-ray
absorbing material is not entirely traced by the HI but is in the form of
ionized hydrogen. Far-ultraviolet absorption line measurements by FUSE are
consistent with this finding and support an ionized hydrogen component towards
the Lockman Hole.
