Social network factors constantly recur as central to explaining initiation, continuation and cessation of substance use and maintenance of long-term recovery. MAP-NET (Measure and Analysis of Personal NETwork) is a computerised instrument for assessing the personal social networks (PSN) of persons with substance misuse and related problems, and it is designed to be used in clinical interviews and to provide relevant measures for research. The article focuses on the conceptual and theoretical framework of MAP-NET and how it is operationalised. The MAP-NET interview makes it possible to identify problems and resources both in general and in relation to the specific circumstances that can be attributed to substance misuse. It provides a basis for a facetted analysis of structural, interactional and functional aspects of PSN—and how these interact. MAP-NET offers possibilities for longitudinal studies on how social networks develop over time and how this relates to substance use as well as to recovery with or without treatment. Implications for network-oriented psychosocial interventions are suggested.