The prognostic value of interim (18)fluorodeoxyglucose positron emission tomography (i-PET) was investigated in 73 patients (median age 60 years) with diffuse large B-cell lymphoma (DLBCL). i-PET was analyzed using the Deauville score (DS) and change in maximum standardized uptake value (ΔSUV(max)). Patients with a DS of 1-3 demonstrated a significantly (p < 0.0001) better outcome (median follow-up 2.4 years) than patients with a score of 4 or 5 in terms of event-free survival (EFS) (79% vs. 36%), progression-free survival (PFS) (84% vs. 47%) and overall survival (OS) (91% vs. 51%). EFS (73% vs. 42%), PFS (78% vs. 50%) and OS (88% vs. 56%) were also significantly (p = 0.023) different between patients with ΔSUV(max) > 66% or ≤ 66%. Patients (n = 33) combining a favorable age-adjusted International Prognostic Index (IPI) (0 or 1) and a negative i-PET either by DS or ΔSUV(max) criteria showed a particularly good outcome (EFS: 85%, PFS: 88%, OS: 94%). Overall, i-PET was highly and independently predictive of any outcome, and its negative predictive value was improved by combination with IPI.