Objectives: Recently, there has been considerable policy and public interest in the availability of over-the-counter (OTC) codeine. Case reports demonstrating severe harm from OTC codeine have been published. However, few studies have examined how people use these products and who develops dependence. The aim of this study was to better understand who develops problematic use of OTC codeine. Design and setting: The authors conducted a web-based survey with people who self-reported OTC codeine use. Eight hundred participants completed the survey that examined codeine use and dependence, pain, and general physical and mental health. Results: Codeine-dependent people differed from nondependent codeine users on a range of characteristics. They were younger, had lower levels of employment and education, and were more likely to report family history of substance dependence. They were more likely to have taken well above recommended doses of OTC codeine and have taken codeine for considerably longer periods of time than recommended. Codeine-dependent people in this study differed markedly from other populations of opioid-dependent people recruited to research in Australia and were more similar to the general population, suggesting that a web-based survey may have reached an under-researched population of opioid-dependent people. Conclusions: How best to use these findings to identify at-risk OTC codeine users requires consideration. Approaches aimed at reducing harm from prescription opioids may be difficult to implement in pharmacy settings. Implications for pharmacists and other health professionals are discussed.