BACKGROUND: Tumors of the thymus are very rare in the pediatric population. This study examines the current trends and outcomes of children with thymus tumors. METHODS: The Surveillance, Epidemiology and End Results (SEER) registry was queried for all patients <20 y of age with primary thymic malignancies from 1973 to 2008. RESULTS: A total of 73 pediatric patients were identified with malignant thymic tumors. The median age at diagnosis was 13 y old. Among the 20 patients that presented with distant disease, 70% died. Conversely, among the 23 patients that presented with locoregional disease, 70% survived. Although the overall mean survival time was 89 +/- 116 mo, 45% of patients died over the study period. Patients with Hodgkin lymphomas and germ cell tumors exhibited the highest survival (76% and 60% at 10 y, respectively). Multivariate analysis was used to identify local or regional tumor stage (odds ratio = 4.5, 95% confidence interval = 1.4-14.5) and surgical resection (OR = 3.8, 95% confidence interval = 1.4-10.8) as independent predictors of survival. CONCLUSIONS: Malignant thymomas and lymphomas are the most common histological variants of pediatric thymus tumors, and patients with Hodgkin lymphomas exhibit the highest survival. Surgery is more commonly performed on malignant thymomas and is an independent prognostic indicator of survival.