The "Down syndrome advantage" is the popular conception that children with Down syndrome are easier to rear than children with other developmental disabilities. We assessed whether mothers of children with developmental disabilities would demonstrate a consistent Down syndrome advantage as their children aged from 12 to 18 years. Results did not reveal significant differences between mothers of children with Down syndrome and mothers of children with other developmental disabilities on most maternal functioning variables. Although the prior group reported a consistent advantage in terms of personal reward and subjective well-being, these diagnostic group differences disappeared when maternal age and child adaptive behavior were controlled. We concluded that these variables may help to explain the Down syndrome advantage.