In drug treatment outcome literature, a focus on objective and socially desirable indicators of change (e.g. no drug use) has predominated, while outcome indicators that are important for drug users themselves (e.g. quality of life, satisfaction with treatment) have largely been neglected. Nonetheless, Quality of Life (QoL) has become an important concept to evaluate effectiveness of treatment in mental health care research and disability studies. Given the almost exclusive focus on Health-related Quality of Life (HRQOL) in substance abuse research and the neglect of clients' perspectives in this field, we explore in this study the concept of QoL as perceived by drug users. Focus group discussions (n = 9) were organised in various treatment settings and community services for drug users in the region of Ghent, Belgium to identify important dimensions of QoL and their interpretation by drug users. Data were clustered and analysed based on the theoretical framework of Robert Schalock (Quality of life. Volume 1: Conceptualization and measurement, 1996). The domains "personal relationships," "social inclusion" and "self-determination" were discussed most frequently by the participants. They stressed the importance of a supportive social network in particular. It can be concluded that QoL is not primarily associated by drug users with health and it involves much more than the aspects typically represented in measures of HRQOL.