This article discusses the recent literature on policy diffusion and puts forward a new articulation of its political dimensions. Policy diffusion means that policies in one unit (country, state, city, etc.) are influenced by the policies of other units. The diffusion literature conceptualises these interdependencies with four mechanisms: learning, competition, coercion and emulation. The article identifies a model of diffusion that is dominant in the diffusion literature. According to this model, policies spread because decision makers evaluate the policy implications of the actions of other units. It is argued that the role of politics remains in the background in this model, and the article shows how going beyond a narrow focus on policy adoptions helps us to consider the politics of policy diffusion more explicitly.