Cystic hygroma is a cystic tumor developed by lymphatic stasis due to congenital blockage of regional lymphatic drainage. It ususally occurs at neck and axilla. However, in some cases of cervical cystic hygroma, cervical portions of the cysts may extend into the mediastinum. We experienced a case of huge cervico-mediastinal cystic tumor in 11 month old girl presenting a large fluctuating neck mass and severe respiratory distress. Surgical resection was done through combined approach of cervical incision and median sternotomy. Pathological diagnosis was confirmed to cervico-mediastinal cystic hygroma.