Background: The type of accommodation provided for persons with an intellectual disability is a major indicator of the social policy for this client group. This is likely to vary within and across countries; hence the importance of undertaking national and international comparisons. Estimations of future need are also required to assist service planning. Method: A database of all persons in receipt of intellectual disability services has been operating in the Republic of Ireland since 1995. In Northern Ireland, regional databases were used to provide similar information. Results: Around 10 000 people live in some form of residential provision: 56% in special settings, 35% in ordinary housing and 9% in hospitals. Most residents were classed as having "severe" disabilities and were aged over 35 years. There were marked differences in the amount and type of provision provided in the two parts of the island. This was also mirrored in differences across health service areas within each country. The demand for future places was greater in Northern Ireland. Conclusions: A planning target of 3.5 places per 1000 adult population is proposed although substantial investments in services is required to achieve this. Longitudinal surveys are an important way of monitoring the impact of new policy initiatives.