  The ROSAT mission gave us the unique possibility to study the galactic
interstellar medium by ``shadowing'' observations on arcmin angular resolution
level. The high sensitivity of the ROSAT PSPC in combination with the large
field of view allows the detailed study of individual clouds, while the ROSAT
all-sky survey is the main source for studies of the large-scale intensity
distribution of the diffuse soft X-ray emission.
  We show that neutral hydrogen clouds are associated with soft X-ray emission,
E(X-ray) < 3/4 keV. These neutral hydrogen clouds, known as high-velocity
clouds (HVCs), are located partly within the galactic halo, and partly in
intergalactic space. The ROSAT detection of soft X-ray emission from some of
these HVCs is the first detection of HVCs in emission other than HI 21-cm line
radiation.
