Little is known about the extent of non-medical use of prescription drugs among European adolescents with substance use disorders. This cross-sectional study examined non-medical use of seven categories of psychotropic prescription drugs (opioid analgesics, ADHD stimulant, sleeping, sedative/anxiolytic, antipsychotic, antidepressant, and anabolic steroid medications) in a clinical sample of Irish adolescents with substance use disorders. Of the 85 adolescents (aged 13-18 years) invited to participate, 65 adolescents (M = 16.3 years, SD = 1.3) took part (response: 74%). Among respondents, 68% reported lifetime non-medical use of any of the prescription drugs; sedative/anxiolytic (62%) and sleeping medications (43%) were more commonly abused. The most frequently reported motives for abuse were "seeking high or buzz" (79%), "having good time" (63%), and "relief from boredom" (56%). Sharing among friends and street-level drug markets were the most readily available sources. Innovative solutions of control measures and intervention are required to address the abuse of prescription drugs.