BACKGROUND Urachus is an embryonic remnant that usually involutes before birth. Abnormal persistence of this structure gives embryologic malformation like an urachal cyst. Infection or malignancy degeneration can complicated it. METHODS Case 1: We report 20 years old female patient consulted with acute abdominal pain. Clinical examination showed fever and infra-umbilical tender mass. The abdominal Computerized Tomography showed pelvic mass between umbilicus and bladder. The open laparotomy found infra-abdominal semi-solid mass. A complete resection was done and histological exam confirmed infected urachal cyst. Case 2: A 19 years old male patient presented with abdominal pain and fever. Physical examination found tenderness in lower abdomen. Biology revealed leukocytosis, and Ultrasonography found a heterogeneous infra-umbilical mass. Surgical exploration by mini-laparotomy found an abscess urachal cyst that is confirm by histological exam after complete resection. Urachal cyst in adult patient is rare. Clinical symptoms without complications are insignificant. Because of malignancy risk, adult urachal cyst are managed by surgery. CONCLUSIONS Infection cyst is the most common complication of urachal cyst. Complete resection is recommended because of malignancy degeneration risk.