The current study looked at illicit methadone use in a group of young people attending a Dublin clinic for treatment of opiate dependence. A structured questionnaire was designed and administered to eligible participants (aged 25 years or under on treatment for opiate dependence). Of the total number of participants (n = 81), 73% reported illicit methadone use before treatment entry and the main reason for use was to manage opiate withdrawals. During treatment 55% reported illicit methadone use and failure to get to the clinic was the main reason given. Some participants reported use for hedonic effects (33% prior to treatment and 12% in treatment). Despite strict controls, most participants reported that illicit methadone was readily available at low cost (EUR 23 per 80 mg). Despite legislative and administrative efforts to curtail methadone diversion in Ireland, we found that it is widespread. Although it is generally used to self-medicate withdrawal symptoms in established opiate addicts, the extent of its use raises concerns as a risk for opiate overdose in the community.