Lymphangiomas, most found in the cervical region, are uncommon benign lesions of the lymphatic system. Pure intrathoracic localization is exceedingly rare and reported as 1% of all lymphangiomas. Here, we report a five year old girl, operated upon for a large intrathoracic tumor mass. The tumor mass was radically removed and microscopic examination was reported as cystic tymphangioma. No recurrence was observed in her follow-up.