The growing body of research showing increased opioid use in patients with chronic pain coupled with concerns regarding addiction encouraged the development of this population-based study. The goal of the study was to investigate the co-occurrence of indicators of addictive behaviors in patients with chronic non-cancer pain in long-term opioid treatment. The study combined data from the individual-based Danish Health Survey in 2010 and the official Danish health and socio-economic, individual-based registers. From a simple random sample of 25,000 adults (16 years or older) living in Denmark, 13,281 individuals were analyzed through multiple logistic regression analyses to assess the association between chronic pain (lasting ⩾6 months), opioid use, health behavior, and body mass index. Six potential addictive behaviors were identified: daily smoking; high alcohol intake; illicit drug use in the past year; obesity; long-term use of benzodiazepines; and long-term use of benzodiazepine-related drugs. At least 2 of the 6 addictive behaviors were observed in 22.6% of the long-term opioid users with chronic pain compared with 11.5% of the non-opioid users with chronic pain and 8.9% of the individuals without chronic pain. Thus, a strong association was demonstrated between long-term opioid use and the clustering of addictive behaviors. An intricate relationship between chronic pain, opioid use, and addictive behaviors was observed in this study, which deserves both clinical attention and further research.