We analyzed the prognostic factors of Korean pediatric patients with supratentorial high-grade glioma (HGG). Between 1997 and 2011, 62 patients with 34 glioblastomas and 28 anaplastic gliomas were surgically operated at nine institutions. The male-to-female ratio was 33 to 29 and the median age was 12 years (range 1-18). The prognostic significance of tumor location, extent of removal, pathologic grade, treatment method, and pattern of recurrence was analyzed. The median progression-free survival (PFS) and overall survival (OS) were 9.3 (± 0.8) and 17.8 (± 1.9) months, respectively. Glioblastoma and anaplastic glioma showed OSs of 15.9 (± 1.3) and 19.6 (± 2.4) months, respectively. Based on the univariate analysis, gross total removal (GTR) and initial combined chemoradiotherapy improved PFS (p = 0.012 and p = 0.003) and OS (p = 0.030 and p = 0.013), respectively. Cerebrospinal fluid (CSF) dissemination showed poor OS (p = 0.001). Based on the multivariate analysis, GTR and initial combined chemoradiotherapy resulted in an improved PFS [(hazard ratio 0.360; 95 % CI 0.177-0.733; p = 0.005) and (hazard ratio 0.458; 95 % CI 0.230-0.911; p = 0.026), respectively]. GTR, initial combined chemoradiotherapy, and no CSF seeding resulted in an improved OS [(hazard ratio 0.417; 95 % CI 0.201-0.861; p = 0.018), (hazard ratio 0.406; 95 % CI 0.206-0.800; p = 0.009), and (hazard ratio 0.288; 95 % CI 0.148-0.563; p = 0.000), respectively]. No significant difference in PFS and OS was observed between glioblastoma and anaplastic glioma. CSF dissemination was observed in 22 patients (35.5 %) during total follow-up. Pediatric anaplastic glioma showed poor survival, similarly to glioblastoma. GTR and initial combined chemoradiotherapy were associated with improved survival.