This study pertains to the development of a web-based, personalized, patient-friendly and easy to administer QoL-instrument for three populations: people with major psychiatric problems, people treated in forensic psychiatry, and people who are supported by homelessness services. The aims of this project are (1) to develop a QoL-instrument called QoL-ME which comprises core QoL domains for policy decisions on an aggregated level and add-on QoL domains for decisions on an individual care planning level, and (2) to conduct an ethical and conceptual analysis of the QoL-ME including the mediating influence of technology. In this project, a holistic point of view is used in the conceptualization of QoL. To this end, Tilburg University, Erasmus University Medical Centre, and RIVM will collaborate with six societal organisations. Every step of the development of the web-based questionnaire will be discussed with patients and other stakeholders. A latent class analysis is used to create core domains and an innovative crowd-based procedure is used to select visual content to represent important life aspects. In addition, focus groups are held to choose relevant add-on domains. A multilevel analysis is conducted to test the suitability of the QoL-ME for individual care planning. Observations/interviews are held to investigate the understanding of the QoL-ME for patients, professional caregivers and policy makers. Moreover, the mediating role of technology is explored by interviewing patients, professional caregivers and other identified relevant stakeholders. This project will result in a better understanding of the Quality of Life of people with severe mental health problems. It elaborates on the existing body of knowledge of this specific population in an innovative and tailor-made fashion.