Providers of public health care are under pressure to involve service-users in service development. This pressure emanates from legislators and the public who promote user involvement (UI), as a 'means to an end' and/or 'an end in itself'. Case studies in six English commissioning areas explored the process and purpose of UI in drug treatment services. In-depth interviews with 139 respondents who commission, manage, deliver or use services were conducted. We identified 'non-', 'passive-' and 'active participant' users. Active users were commonly motivated by a desire for social justice, a social conscience and personal development. UI was evidently influenced by multiple social organizational and personal factors. Some 'generic' factors have been reported in other settings. However, the illegality of drug use powerfully affects all stakeholders creating a context unique to drug treatment settings. Stigma and power imbalances were pervasive, and strong tensions concerning the goal and purpose of UI were apparent. Within the UK context, we identified five organizational approaches to UI. Based on rationale and objectives of UI, and the scope of influence accorded users, organizations could be characterised as protagonists, pragmatists, sceptics, abstainers or avoiders. We conclude that many tensions apparent in local level UI have roots in UI policy, which is ambiguous about: (1) benefit and rights, and (2) the promotion of healthcare objectives within a UK drug strategy driven by a crime reduction agenda. This duality must be resolved for UI to flourish at local level.