Regarding primary mediastinal large B-cell lymphoma (PMLBCL), there are several controversial topics that warrant further investigation: the superiority of third-generation regimens, the impact of rituximab, the use of involved field radiotherapy (RT) and the assessment of clinical response by positron emission tomography (PET). We report our experience on 74 PMLBCL patients treated with a combination of a third-generation chemotherapy regimen (MACOP-B) and rituximab: an observational retrospective single-centre study was conducted on patients diagnosed and treated between February 2002 and July 2011. All patients were evaluated by computed tomography scan and PET scan; after the final PET evaluation, PET-negative patients were observed, whereas PET-positive patients underwent mediastinal RT. Sixty-one (82.4%) patients achieved a complete response after the MACOP-B plus rituximab regimen; 68.9% presented a positive final PET and were treated with local RT, whereas 31.1% had a negative PET. Five patients relapsed within 12 months. At 10 years, overall survival was 82%, progression-free survival was 87.6% and disease-free survival (DFS) was 90.5% (median follow-up 4 years). No statistically significant differences were observed in DFS between the patients treated also with RT (PET positive) and patients only observed (PET negative): 90.7% vs 90% (p= 0.85), respectively. In our experience, adding rituximab does not change the final results in terms of complete response and DFS utilizing third-generation regimen. Furthermore, the introduction of the PET-guided RT approach leads to a patient-tailored treatment, which preserves the outcome and, at the same time, allows reducing the use of RT. Copyright © 2014 John Wiley & Sons, Ltd.