This article presents the results of an international survey of treatment programmes for drug and alcohol abusing offenders throughout the European Union. Questionnaires on 86 programmes were collected from 27 EU countries. They captured data about programme design, delivery, administration, infrastructure and other features. Most programmes targeted any level of substance abuse. We observed many types of treatment modality across Europe. There was a preference for cognitive behavioural and non-behavioural programmes over pharmacological treatments and therapeutic communities. Governments provided the funding for almost all the programmes. Practitioners noted that maintaining client motivation was central to realising effective treatment delivery. Most respondents indicated that some basic process evaluation data were gathered to help maintain treatment fidelity. However, methodologically sound outcome evaluations of programme effectiveness were rare. The findings reveal discrepancies between routine practice and the results of international evaluation research. They clearly underline the need to integrate evaluation into routine practice and for greater use of evidence-based policies across the continent.