Background Based on national registers, the prevalence of intellectual disability (ID) in Norway is estimated to be 0.44 per 100 inhabitants. This study aimed to examine geographic and urban–rural differences in the prevalence of ID in Norway.
Methods A survey based on the national register. Financial transfers intended to provide equal services to people with ID are based on these reports.
Results A higher prevalence was found in the North region of Norway. A negative correlation between the population density and the prevalence of ID was also found.
Conclusion There was considerable geographic and urban–rural differences in the prevalence of ID, which may be attributable to not only the large diversity of services, but also some other factors. The results were discussed with respect to the deinstitutionalisation progress, resource-intensive services and costs. Differences also reflect some problems in diagnosing ID in people having mild ID.