The aim of this study was to examine the influence of user, staff and work unit characteristics on addiction care practitioners’ assessments of the severity of alcohol and drug use. A factorial survey was conducted among 489 social workers, therapists, nurses, doctors and executives from 77 addiction care units in the three largest Swedish counties. Staff assessed the severity of 10 fictive scenarios, vignettes (n = 4724), describing persons with varying social characteristics who were users of alcohol, cannabis or cocaine. The effects of user, respondent and work-unit variables on the practitioners’ severity assessments were estimated using multilevel regression analysis. The results show that perceived severity was influenced not only by the substance, the frequency and character of the negative consequences of the use, but also by the age, socio-economic status and family situation of the user. Women, older respondents and respondents with a medical education rather than a social work education were on average more inclined to assess the vignettes as being more severe. Analyses of various interactions revealed that practitioners viewed the drinking of young men as being less severe than that of young women. Doctors saw women's use as more problematic than men's, irrespective of the context. To conclude, alcohol and drug consumption is judged by different norms, depending on various characteristics of the users, of the practitioners and also of their workplaces. To avoid potential negative consequences of the application of such varying standards in addiction care, more individual reflection and workgroup discussion are needed.