  Observations of dark cloud cores have been carried out in the mid-infrared
using ISOCAM and in the far-infrared using ISOPHOT, both aboard the Infrared
Space Observatory. The cores are in most cases detected in emission at 200 and
170 micron, remain undetected at 90 micron and are seen in absorption against
the diffuse mid-infrared background at 7 micron. The observations are
consistent with the cores being pre-stellar and not having a central heating
source, and yield core temperatures of ~ 11-13 K. We were able to determine the
density structure of the cores up to radii that extend beyond the sensitivity
limit of previous submillimetre studies. The column density profiles of the
cores studied here flatten out in the centre, as shown by previous
submillimetre continuum results, and interestingly, in a few cases, the
profiles steepen with radius beyond ~ 5000-10000 AU and present sharp edges.
This could indicate that these cores are decoupled from their parent molecular
cloud and represent finite reservoirs of mass for subsequent accretion.
