Aim To provide new insights into heroin users' eating patterns in order to inform nutritional interventions. Design Seventy-seven audio-recorded in-depth interviews which elicited detailed data on eating patterns. Setting Community and residential drug services, pharmacies and peer support groups in Southern England, UK. Participants Forty current or ex-heroin users (21 men and 19 women), of whom 37 (20 men and 17 women) were re-interviewed after 3 months. Measurements Audio data transcribed verbatim, coded systematically and analysed inductively. Findings Heroin users' eating patterns were influenced by individual, social, cultural, economic and environmental factors. During active heroin use, participants consumed quick, convenient, cheap and sweet foods, ate infrequently and had little interest in food. Eating patterns often improved during stays in residential services and after heroin cessation. Ex-heroin users began to take pleasure in food preparation and eating and identified therapeutic benefits to cooking. Initially, weight gain was experienced positively, but subsequently generated anxieties as participants, particularly women, struggled to control their appetite and worried about becoming overweight. Findings complement and add to previous research and sociological and anthropological literatures. Conclusions Heroin users have dysfunctional eating patterns that are amenable to change and community and residential services could enable them to experience the many health, psychological and social benefits of improved eating practices. Nutritional interventions need to be tailored to individual needs and circumstances, but also monitored and evaluated so that there is a future evidence base.