This chapter introduces the EQUAL project, which examined the legal capacity and self-determination of people with intellectual and psychosocial disabilities in Portugal. It critiques the historical linkage of citizenship to mental capacity and highlights the UN CRPD’s Article 12, which calls for equal legal recognition for all and supported decision-making. Despite reforms like Portugal’s Law 49/2018, practical barriers persist: medicalized capacity tests, substituted decision-making, and attitudinal, institutional, and structural barriers. The EQUAL study adopted an interdisciplinary framework, drawing on theoretical insights from both sociological and legal scholarship. Methodologically, it combined court decisions analysis, interviews, focus groups, and six life stories using participatory methods to center disabled people’s voices. The plan of the book is described.