Objective To evaluate the potential ability of 18F-FDG PET/CT delayed imaging of pelvis for detection and locoregional staging of urinary bladder tumors. Methods Twenty-seven patients suspected with primary carcinoma of the urinary bladder were evaluated prospectively for diagnosis and staging. The patients underwent conventional contrast-enhanced computed tomography (CECT) of the pelvis and whole-body 18F-FDG PET/CT. In addition, delayed pelvic PET/CT images were obtained after oral hydration. Results of CECT and 18F-FDG PET/CT were compared considering histopathology as a reference standard to evaluate the value of delayed pelvic PET/CT images in detection and locoregional staging of urinary bladder tumors. Results Of the 27 patients, the sensitivity of CECT and delayed pelvic PET/CT was 77.27% and 90.90% respectively; the specificity was 60.00% and 40.00% respectively; and the accuracy rate was 74.07% and 81.48% respectively. The accuracy rate of delayed pelvic PET/CT imaging and CECT had no statistical difference (P=0.263). Twelve patients underwent radical cystectomy, ten had locoregional metastases. The accuracy rate in locoregional staging of CECT and delayed PET/CT was 33.33% and 91.67%, respectively. Delayed PET/CT was superior to CECT (P=0.018). Conclusion 18F-FDG PET/CT delayed imaging of pelvis has a good sensitivity and accuracy rate in detection of urinary bladder cancer as good as CECT, and might be more better in locoregional staging of urinary bladder cancer.