Soft X-ray images of interstellar gas clouds at high galactic latitudes obtained with ROSAT show a count rate distribution which is anti-correlated with HI or molecular tracer of their total gas column densities, i.e., they display what are called "X-ray shadows". These shadows are used to derive the properties the soft X-ray halo of our Galaxy. Superimposed X-ray bright spots are often found to be associated with HI high velocity clouds (HVC) exhibiting signatures of inelastic collisions with other gas clouds. The new Leiden/Dwingeloo Survey of galactic HI indicates faint emission of very high velocity dispersion in the galactic halo. Densities derived for these tracers of plasma and gas in the halo (z > 3 kpc) are in the range 10**-3 cm**-3 to 0.3 cm**-3, i.e., rather larger than conventional numbers.