Background. - Cystic retroperitoneal lymphangioma is a rare benign tumor with Case reports. - Case 1. A girl was born at term after ultrasonography had shown a cystic abdominal mass by 31 weeks of GA. This mass, clinically palpable at birth, was found again by ultrasonography. Surgical excision on day 3 was incomplete, requiring a second excision at the age of 2 months, followed by persistence of the cyst near the bladder; the patient was asymptomatic at the age of 2 years. Case 2. This full-term female newborn was admitted because of jaundice and pallor. Examination showed a firm mass of the left flank that was confirmed by X-rays and ultrasonography. Despite blood transfusion, anemia persisted, requiring surgery that showed a cystic hemorrhagic mass that was voided. A second partial excision was performed a few weeks later and, at the age of 7 months, ultrasonography showed a few small cystic masses behind the left kidney. Case 3. A 16-month-old boy was operated on for right inguinal hernia. The hernial sac contained fluid and its wall was thick. Ultrasonography and CT scan performed 3 days later were normal. The child was examined again 28 months later because he suffered from abdominal pain; a large mass was palpable in the right flank that appeared cystic at ultrasonography and CT scan. A retroperitoneal lymphangioma was completely excised. Conclusion. - Because the risk of complications is apparently high, surgical treatment is always necessary. In the newborn period, complete excision is difficult, requiring delayed surgery.