  The recent detection of dust emission in Complex C, the largest High-Velocity
Cloud (HVC) on the sky, opens a very interesting perspective for Planck. The
HVC dust temperature determined using IRAS and Spitzer observations is low
(T~10.7 K) in accordance with its great distance from the Galaxy (> 5 kpc).
Peak column density in 30 arcmin beam is NH ~10^20 cm-2 which is typical of
HVCs and similar to cirrus column density in diffuse regions. On the other hand
HVCs appear to be very clumpy at smaller angular scales; several observations
at the arcminute scale resolution show significant structure and higher
brightness contrasts than in typical cirrus emission. In this contribution we
show that, even with their moderate column density, the cold temperature, high
emissivity and high column density contrast of HVCs should lead to significant
and detectable emission in the Planck-HFI frequency range. In order to separate
the HVC emission from the Galactic cirrus emission, the use of 21 cm
observations will be mandatory.
