Internationally, service user involvement has become a common feature of public policy and more specifically public health policy in the recent decades. In a general context, the involvement of service users in health services has been well documented; however, less evidence is available within the area of drug treatment service provision. This study, which was conducted in Ireland, sought to address this gap in the knowledge and understanding of service user involvement within this setting. Qualitative in-depth interviews were undertaken with a broad range of participants. The sample, which totalled 20 individuals, comprised both service users and service providers. Meanings, and mechanisms of and limits to user involvement were explored. This study highlights the ambiguity that exists between policy recommendations on service user involvement and actual practice within treatment services. Although, participants acknowledged that services could and should learn from the individual and collective experiences of service users, they were found to be passive players in planning, developing, evaluating and delivering the services they received. The study suggests that in order to change the rhetoric of policy recommendations into a reality within this context, a much more committed approach which includes the education and training of all involved in drug treatment services is required. (Contains 2 notes.)