Ageing (55+ years) mothers of adults with intellectual disabilities in the Republic of Ireland, Northern Ireland and the United States were compared with respect to three general issues. Firstly, to what extent do the adults in these three countries differ in their level of reliance on their mothers? Secondly, do the mothers differ in the extent to which they have made plans for the future care of their son or daughter with intellectual disabilities? Thirdly, do the mothers differ in physical, social and psychological well-being? These cross-national comparisons were undertaken to examine the extent to which lifelong caregiving has either a common influence on mothers across national boundaries, or, alternatively, whether the cultural context exerts a unique influence on mothers in each country. Findings supported the latter explanation, even when background characteristics were statistically controlled.