AbstractThe results of drillings in dome-shaped palsas are presented. A comparison of the internal structures of these palsas and of previously investigated pingos in northernmost Sweden indicates that the processes of formation may have been similar. Drillings have also shown, that today the ground surrounding the pingos is unfrozen. However, as there are indications of former more common permafrost within the pingo area, as well as in northern Scandinavia in general, it is not unlikely that the pingos date from a period when permafrost was more widespread.