A 90-year-old female was diagnosed with diffuse large B-cell lymphoma. F-18 FDG PET /CT scan was suggested for decision making in treatment planning and complete staging. The PET/CT images showed an unusual dumbbell appearance of activity in the pelvis with increased FDG uptake on 1.5 hour images. The delayed images in PET/CT scanning revealed that the bladder was with normal FDG activity on its normal position. According to the two PET /CT results, the patient had a sliding bladder, located at both sides of the pubococcygeal line, with a intermittent grade III cystocele.