© 2014, Indian Society of Haematology & Transfusion Medicine. We retrospectively analyzed the prognosis of patients with diffuse large B cell lymphoma (DLBCL) and a bulky mass at diagnosis. We retrospectively analyzed clinical data for 29 consecutive DLBCL patients with an initial bulky mass receiving R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone) therapy from 2004 to 2011. Bulky disease was defined as a measurable tumor mass >10 cm in diameter or a mediastinal mass >1/3 of the chest diameter. Patients with primary mediastinal large B-cell lymphoma were excluded. The median age was 65 years (20–78 years) and the maximum tumor diameter was 11.5 cm (10.0–17.0 cm). Complete response and partial response were achieved in 14 patients each, while 1 patient had progressive disease. The 3-year overall survival (OS) rate and progression-free survival (PFS) rate were 66 and 56 %, respectively. Findings on post-treatment positron emission tomography-computed tomography (PET–CT) were significantly associated with OS (34 % for patients with abnormal uptake vs. 75 % for those without, P = 0.014), and were also associated with PFS (36 vs. 83 %, respectively, P < 0.001). Nine patients with a single site of abnormal uptake on PET–CT underwent radiotherapy and 5 of them subsequently relapsed. An initial bulky mass does not indicate a poor prognosis of DLBCL. However, the post-treatment PET–CT findings may have predictive value in DLBCL patients with a bulky mass.