Background: Optimism and pessimism are positive and negative expectations linked with well-being in adults. Research on the importance of optimism and pessimism in children is limited by the lack of a developmentally appropriate measure of children's expectations. Method: Based upon the Life Orientation Test-Revised (Scheier, Carver, & Bridges, 1994), the Youth Life Orientation Test (YLOT) is a sixteen-item self-report measure of children's optimism and pessimism. Results: Reliability and validity of the YLOT was found with 204 3rd-6th graders. Optimism also predicted fewer child-reported depressive symptoms and parent-reported behavior problems assessed three months later. Pessimism predicted more child-reported anxiety symptoms and parent-reported social and academic deficits.