Due to highly sensitive detectors and to the observers' efforts the observations of high galactic latitude clouds (HLC) have been improved in the last few years. The detection of infrared cirrus clouds, which were discovered by the IRAS (Low et al. 1984), strongly stimulated research on HLC. It is generally considered that HLC are small clouds which lie around 100 pc of the Sun (Blitz et al. 1984). This idea is consistent with their small velocity (VLSR) in the CO (λ = 2.6 mm) line.