Background: In people with ID there is more morbidity than in the general population, including cardiac diseases. Dutch figures on this subject are scarce. Methods: Descriptive study of the prevalence of cardiac diseases in 436 residential clients in Echt, the Netherlands, and comparisons between men and women, age groups, and level and aetiology of ID, were carried out. Results: It was found that the total prevalence of cardiac diseases was 14%, with a higher prevalence among women, the elderly, and people with mild/moderate ID. Conclusions: The prevalence of cardiac diseases in residential clients is substantial. With the increasing number of ageing people with ID and people with ID living more independently in community-integrated residences, it is expected that the morbidity and mortality from cardiac diseases will increase further.