Primary Mediastinal large B-cell Lymphoma (PMLBL) is a rare entity predominantly affecting adolescents and young adults. Recently, an international phase 2 trial in pediatric patients using dose-adjusted etoposide, doxorubicin, and cyclophosphamide with vincristine and prednisone plus rituximab (DA-EPOCH-R) failed to reproduce excellent survival reported in some adult studies. The optimal therapy regimen needs to be determined in this disease. French prospective LMB2001 trial included all patients < 18 years with mature B-cell lymphoma treated in French centers. For patients with PMLBL, treatment included 4 to 8 courses of Lymphomes Malins B (LMB)-based chemotherapy without radiotherapy. From 2008, rituximab was added before each chemotherapy course. From 09/2001 to 03/2012, 42 patients with PMLBL were registered. The median age was 15 years (range 8-18). 21 patients were treated by chemotherapy plus rituximab. The median follow-up was 7.1 years (Interquartile range, 5.8-11.1). Five-year event-free (EFS) and overall survival (OS) were 88.1% (95%Confidence Interval (CI), 75.0%-94.8%) and 95.2% (95%CI, 84.0%-98.7%) for the whole population. The 5-year EFS was 81.0% (95%CI, 60.0%-92.3%) and 95.2% (95%CI, 77.3%-99.2%) (HR=0.24 (95%CI 0.03-2.2)) and 5-year OS was 90.5% (95%CI, 71.1%-97.3%) and 100% for patients treated without and with rituximab, respectively. Only 1/21 patients treated with rituximab and LMB-based chemotherapy had local early treatment failure but achieved prolonged complete remission with second-line chemotherapy and radiotherapy. Intensive LMB-based chemotherapy with rituximab achieved excellent survival in children/adolescents with PMLBL. Further international prospective studies are required to confirm these results in this population.