BACKGROUND: We aimed to describe, among a population of women with intellectual disabilities (ID) living in institutions in France, the characteristics in whom breast cancer (BC) was diagnosed and of those who participated in BC screening. METHODS: Study was performed in 2009 among a random, representative sample of women with ID living in institutions in France. Participants answered a questionnaire either directly by themselves, or with the help of an intermediary. RESULTS: In total, 978 women with ID aged over 18 years were included, and 14 were diagnosed with BC. The incidence observed in this sample of women with ID is similar to that of the general population (standardised incidence ratio, SIR 0.857, 95% confidence interval (CI) 0.42-1.53). Average age at diagnosis was 47.8 years, and the risk of developing BC before the age of 50 was 2.03% (0.4-3.66). This risk was not significantly different from that of the general population (2.4%, 1.0-3.78). Obesity was almost twice as frequent in women who had BC as compared to those without BC (43% vs. 22.5%, P = 0.0196). Among the 310 women aged >50 years and eligible for the national BC screening programme, 238 (77%) had already had at least one mammogram, and 199 had had it within the previous 2 years. Adherence to the screening programme was 64.2% (199/310) in the participating institutions. This rate was slightly higher than the national average of 62% for the same period. CONCLUSIONS: The results of this study show that BC is equally as frequent among women with ID living in institutions as in the general population, and occurs at around the same age. Obesity was significantly more frequent among women in whom BC was diagnosed in our study. Participation in BC screening is slightly higher among women with ID living in institutions than among the general population.