Endometriosis is a common disease affecting mostly women in childbearing age. It usually involves the internal pelvic organs but occasionally can present in unusual locations. We report on a 32-year-old nulliparos female presenting with a suburethral painful mass causing obstructive voiding symptoms; she had also a long history of dismenorreia, perimenstrual pelvic pain, urinary tract infections, disúria and dispareunia. The diagnostic work-up revealed a suburethral cystic lesion consistent with a complicated urethral diverticulum or a suburethral endometrioma. Complete surgical excision confirmed an endometriotic cyst. The differential diagnosis of this rare suburethral location of endometriosis with other vaginal cysts is discussed.