The aim of the chapter is to present stakeholder theory and provide some examples of how it may be applied in the field of addiction policy. The paper arises from research conducted as part of the ALICE RAP project, a large multidisciplinary European programme (http://www.alicerap.eu). Case studies conducted in five countries (Austria, Italy, Denmark, Poland, and the United Kingdom) examined stakeholder dynamics and the relationships between stakeholders in the drug and alcohol policy arenas. The chapter is divided into three main sections. The first section examines the stakeholder concept and presents different theoretical perspectives on stakeholders and stakeholding. The next section describes and discusses different types of stakeholders within the addiction policy field. The third part of the chapter illustrates key themes using case studies of stakeholding in substitution treatment from the five countries mentioned.