Research on co-creation often appears unclear, encompassing various definitions and blurred boundaries between related concepts and phenomena. This chapter aims to explore different approaches to understanding and studying co-creation within welfare services, focusing on the role of users. The chapter draws on an analysis of different conceptualizations of the co-creation concept as it appears in the literature. It highlights specific contributions and influential authors who have made significant impacts in the field, and the related discussions that have shaped its development. We identify three distinct approaches to the concept of co-creation: “co-production”, “co-creation of innovation”, and “co-creation of value”. These approaches share the view that users’ and citizens’ knowledge is crucial for offering and developing effective welfare services, and that co-creation involves active participation from users and citizens. However, they differ in terms of the objectives of co-creation, positioning users as “co-producers”, “innovators”, and “value creators”, respectively. We demonstrate how this distinction could help clarify and frame co-creation in research, policymaking, and practice.