How do people on opioid substitution treatment differ from other opioid users as patients? Niklas Mäkelä Airi Partanen Hannu Alho Kristiina Kuussaari Kuva 1 / 3 Background Opioid substitution treatment (OST) has been offered in Finland for over twenty years. The number of patients has steadily increased in the 21st century. In 2015 approximately 3 300 patients were in OST. The objective of this study was to obtain more information about OST and patients in OST. Methods The analysis is based on the 2015 survey on intoxicant-related cases. In the survey all social and healthcare units filled in a questionnaire on any intoxicant related cases during the 24 hours of data collection. In this study 10 844 intoxicant related cases were divided into three groups: patients in OST, other opioid users in the treatment system and other substance users in the treatment system. Results Altogether 1 585 patients in OST were documented. Patients in OST and other opioid users were younger, had more polydrug use and more lifetime intravenous drug use than other substance users. The majority of patients were in the HUCH hospital district. Patients in OST received less services (excluding maintenance treatment) than the other groups. Conclusions The survey captured 48% of the estimated number of patients in OST. Comparing patients in OST and other opioid users the beneficial effects of OST can be observed in this study.