A natural experiment contrasted the self-rated well-being of people with intellectual disabilities (n = 75) and those with enduring mental health problems (n = 44) after they moved to new accommodation and support options, while others remained in congregated settings or living in the family home. Most support staff also provided well-being ratings. In personalized arrangements, personal well-being was significantly higher than in congregated settings; particularly for people with intellectual disability who had higher support needs compared to people with mental health problems. Moving to a group home also brought some improvement in the well-being ratings of people with intellectual disability but only for those with higher support needs. Such moves seemed to lead to a decline in well-being for those with mental health problems. There were marked discrepancies between ratings given by the person with those of staff. The well-being measure shows promise for use in further comparative and longitudinal studies.