To evaluate the role of FDG-PET/CT in detecting bone marrow (BM) involvement, pre-treatment bilateral bone marrow biopsies (BMBs) and FDG-PET/CT scans of 89 patients with diffuse large B-cell lymphoma (DLBCL) treated with rituximab-CHOP were reviewed and analyzed. Fourteen patients (15.7%) had lymphomatous involvement based on BMB (BMB+), and 17 patients (19.1%) had the possibility of BM involvement on FDG-PET/CT (FDG-PET/CT+). Seventy-two patients (80.8%) had concordant results between BMB and FDG-PET/CT (seven patients were positive for both, and 65 patients were negative for both), but 17 patients (19.2%) had a discordant interpretation (seven patients were BMB+ and FDG-PET/CT-, and ten were BMB- and FDG-PET/CT+). Although BMB+ patients had an inferior 2-year EFS (37.0% vs. 79.8%, p < 0.001) and OS (36.3% vs. 81.0%, p < 0.001) compared to BMB- patients, no differences in EFS (62.6% vs. 72.7%, p = 0.185) and OS (59.4% vs. 78.0%, p = 0.146) were shown between FDG-PET/CT+ and FDG-PET/CT- patients. Whereas six of seven patients with diffuse hypermetabolism were BMB+, only one of ten patients with focal hypermetabolism was BMB+. The results suggest that FDG-PET/CT had a limited value to detect BM involvement in patients with DLBCL. Focal hypermetabolism of hematopoietic BM in FDG-PET/CT had no impact on survival.