Background: To date, there has been no published comprehensive estimation of costs related to Prader-Willi syndrome (PWS). Our objective was therefore to provide data on the economic burden and health-related quality of life associated with PWS in France in order to raise awareness of the repercussions on individuals suffering from this syndrome and on caregivers as well as on the health and social care systems. Method: A retrospective cross-sectional study was carried out on 51 individuals recruited through the French PWS patient association.