A 69-year-old woman diagnosed with Waldenström macroglobulinemia (WM) was referred for F-FDG and Ga-Pentixafor PET/CT for evaluation of the disease. Extensive involvement of WM with intense radioactivity in the bone marrow and lymph nodes was found in Ga-Pentixafor PET/CT. However, in F-FDG PET/CT, the lesions showed significantly lower tracer uptake. Given the superiority of Ga-Pentixafor in detecting WM lesions to F-FDG in this patient, Ga-Pentixafor PET/CT might be a promising imaging modality in assessment of tumor burden of WM in future studies.