Abstract: Aims Most people appear to stop using cannabis when getting older, but a certain subgroup becomes cannabis dependent, has problems in various life areas and needs treatment. Our aim is to compare a number of sociodemographic and treatment seeking variables between treatment seekers with primary cannabis problems and those with primary alcohol, opiate, amphetamine or cocaine problems. Understanding how primary cannabis users seeking treatment differ from other treatment seekers may assist clinicians in better tailoring treatment processes to clients needs. Methods For this purpose, intake information on 1,626 persons seeking treatment in one of 16 treatment agencies in the province of Antwerp ( Belgium) was registered via an on-line web application. Primary cannabis users seeking treatment were compared with primary alcohol, opiate, amphetamine and cocaine users by means of bivariate analyses (Chi-square tests and analyses of variance), followed by four logistic regression analyses. Findings 14.5% of all clients used cannabis as their primary drug. Compared to primary alcohol, opiate, amphetamine or cocaine users seeking treatment, cannabis users seeking treatment appeared to be more often male, younger than 30 years old, Belgian and student. They are often referred to treatment by police or justice and 43.6% of them can be considered single-substance users. Multivariate analyses showed that besides age and sex, using no other substances than the primary drug and being registered in outpatient facilities only were significant determinants for being a primary cannabis user seeking treatment. Conclusions Primary cannabis users can clearly be differentiated from other drug users seeking treatment. Although cannabis plays an important part in a polydrug use pattern, persons who have cannabis as their primary drug often use only this one substance. Since they regularly have brief contacts with treatment agencies, more research is needed to measure the effect of this brief intervention.