The high prevalence of sleep disorders, particularly obstructive sleep apnea, is well established in children with Down syndrome. However, only a few studies have focused on older children and young adults in this population. Given the presence of sleep disorders and the early emergence of Alzheimer's disease, more work is needed to examine the relationship between sleep and cognition in Down syndrome. Twenty-nine adolescents and young adults with Down syndrome participated in the present study. Parents reported on their sleep difficulties using a well-validated measure of sleep problems in intellectual disabilities. Based on theoretical models linking obstructive sleep apnea to prefrontal cortex dysfunction, we tested components of executive functions that have been shown to be impaired in previous studies of Down syndrome. First, results indicate that participants with Down syndrome with higher body mass index also had increased caregiver reports of sleep apnea symptoms. Individuals with high ratings of sleep disruption also showed greater difficulties with executive function. These results suggest that sleep disruption may place this set of functions at risk in young adults. Future work should examine if this risk may result in earlier onset of dementia or steeper decline with Alzheimer's disease. Further, additional studies are needed to investigate the effect of exercise interventions and weight reduction on sleep disorders in this population. (Contains 2 tables and 1 figure.)