Taking a step forward from the IPI, attention is focused on the role of 18F-FDG PET/CT as a tool for guidance in risk stratification in patients with aggressive non-Hodgkin's lymphoma (NHL). Here, we analyzed the predictive value of various PET/CT parameters in patients with DLBCL. Particularly, we were interested in patients with an IPI score of 1, 2, or 3, whose prognosis are confusing. Between Jul 2008 and Feb 2010, a total of 100 patients (including 57 patients with an IPI score of 1-3) who were treated with R-CHOP for DLBCL, and had assessable PET/CT parameters were analyzed in this study. Absolute value of SUVmax, SUVsum(sum of SUVmax) and TLGsum(SUVmean x Volumemeta) from baseline and interim PET/CT, and ΔSUVsum, ΔSUVmax, and ΔTLGsum between baseline and interim PET/CT were selected as PET/CT parameters. The median number of R-CHOP cycles was 6, and interim PET/CT was performed after 2 or 3 cycles. None of the parameters which showed percentile change between initial and interim PET/CT were associated with prognosis. Instead, absolute value of SUVsum from baseline PET/CT, and SUVmax and SUVsum from interim PET/CT were significantly relevant to PFS in all patients, and in patients with an IPI score of 1–3.