Findings about the influence of coping on psychological adjustment in children with different medical conditions are inconsistent and often based on cross-sectional data. This prospective study evaluated the effect of various coping strategies on children's post-traumatic stress symptoms and behavioral problems 1 month and 1 year after an accidental injury or the diagnosis of a chronic disease in 161 pediatric patients 6-15 years of age. Only minor positive effects of coping on psychosocial adjustment were found: Religious coping reduced post-traumatic stress symptoms. Active coping strategies had negative effects on internalizing and externalizing behavioral problems. Support seeking strategies, distraction, and avoidance had no impact on long-term psychosocial adjustment.