Urinary retention due to bladder diverticulum is a rare clinical entity. We report Three males that were subjected to transurethral resection of prostate due benign hyperplasia with urinary retention, after removal of the catheter during postoperative period, requiring a new catheterization, and an adolescent woman with history of urinary infection that presented urinary retention four previous months to her first interview in the service. The later investigation demonstrated in all patients a big bladder diverticulum. The diverticulectomy reestablished the satisfactory bladder emptying in all patients. The origin of the bladder diverticula, the mechanism of the urinary retention without obstruction and its treatment is discussed.