Background: Patients receiving buprenorphine who are poor responders can continue to commit drug-related offences. Switching them from buprenorphine to methadone may result in reduced criminal behaviour. We compared self-reported offences and incarceration before and after starting methadone treatment of patients switching from buprenorphine (PSB) and maintenance treatment incident users (MIU). Methods: Data on offences, incarceration and other information, were obtained via a telephone interview. Mixed models were used to assess the impact of methadone initiation and being PSB or MIU on (1) the number of days when offences were committed (drug sale, drug purchase, other offences) and (2) experiencing incarceration during the previous 6 months. Results: Among the 176 patients with at least one assessment for self-reported offences, 51.7% were PSB. Receiving methadone was significantly associated with a reduction in the number of days when drug sale or drug purchase offences were committed, but not other offences. PSB and MIU groups were different only for drug purchase, as PSB were more likely to have a higher number of days of drug purchase from month 3 onwards. A reduction of 77% in the likelihood of experiencing incarceration was observed and this was comparable in PSB and MIU. Conclusion: Switching non-responding buprenorphine patients to methadone can result in a major reduction in offences and incarceration rates. Increasing access to methadone, using more flexible models of care is urgent for clinical and public health reasons. ã