Background: The JPLT3-S (Japanese study group for Pediatric Liver Tumors) 3 study, conducted cisplatin (CDDP) monotherapy for young children (< 3 years old) with standard risk hepatoblastoma (HB) evaluated central review system in Japan. In the previous JPLT2 study, cases with resectable tumors without any annotation factors in the PRETEXT classification (standard risk HB) showed favorable outcomes by the therapies consisted of CDDP and pirarubicin, but showed toxicities and late complications. In this JPLT3-S trial, less intensity regimen consisted of CDDP alone were evaluated in the young children (< 3 years old) with standard risk HB. Methods: Patients who were less than three years of age, who had PRETEXT I, II, or III HB without any annotation factors (e.g., E1, E1a, E2, E2a, H1, N1, P2, P2a, V3, and V3a) were eligible for inclusion in this study. In this trial, we introduced central radiological and pathological reviews of all patients. The primary outcome was 3-year progression-free survival (PFS). Results: A total of 38 patients (23 female) were included. The median patient age was 12 (range, 2-34) months. Two patients discontinued treatment because of progressive disease, and five patients discontinued treatment for other reasons. The 3- year PFS rate was 93.9% (95% confidence interval [CI], 86.4 to 100). All 38 patients survived (follow-up period 38-98 months), and the OS rate was 100% (confidence interval, 100). There were no cases with late complication without ototoxicity. Conclusion: CDDP monotherapy regimen is feasible in young patients with localized HB classified by central review.