Findings are presented from a survey of a sample of 2641 UK school students aged 15--16 years. This exercise was part of the 30 country European School Survey Project on Alcohol and other Drugs (ESPAD). The 201 students who reported using cannabis (marihuana) 40 times or more were examined using cluster analysis. They were also compared to other students. Three clusters of heavy cannabis users emerged. The smallest was largely distinguished by antisocial behaviour. Another cluster were clearly unhappy, with little support from parents and friends, high levels of depressed mood and low levels of self-esteem. The largest cluster were 'ordinary' and had little to distinguish them apart from a belief that their environment was stable and predictable and that society's rules should be obeyed. Although clear relationships emerged between heavy cannabis use and heavy use of other substances, the 'ordinary' cluster of heavy cannabis users were less likely than the others to have used other illicit drugs. It is therefore concluded that teenage heavy cannabis users have varied motivations and contexts for their usage. They should not be seen as a homogeneous group and many do not appear to use other illicit drugs.