AbstractAlthough rare diseases concern a small fragment of the population, they collectively affectabout 4% of the general population. The well-being of patients with rare diseases has longbeen overlooked, but several scales now measure their health-related quality of life(HRQoL), enabling targeted cures and interventions. However, not all scales are equallyefficient at measuring key aspects of quality of life of patients. In the present study, weevaluate health related quality of life (HRQoL) scales for rare diseases from the perspectiveof the social science-driven field of quality of life (QOL). Using the method of Booysen toevaluate social indicators, we review eleven scales frequently used in the case of rarediseases (CFQ, CFQoL, DLQI, MOS, PLC, QLI, SF-12, SF-36, SIP, Skindex, TAAQOL) and mapwhat is measured and what is not. Key findings are that scales are overly focused on outputbased specific indicators, lack flexibility, and miss a holistic view of quality of life. Wesuggest improvements such as incorporating more generic items, including inputindicators, targeting general well-being, and involving patients in the development ofquestions.Keywords: Rare diseases, HRQoL, QOL, well-being, scales, evaluation