. Sleep problems have been related to several behavioral disorders. In the last few decades, growing attention has been given to externalizing problem behavior. Previous work has indicated that children and adolescents presenting externalizing problem behavior are at risk for an array of disorders in adulthood, including anxiety, disruptive behavior, mood problems and substance use. Several studies have shown that sleep problems may be related to externalizing problem behavior; research however is limited, especially among children younger than 18 months.