Abstract. Lymphatic malformations account for approximately 5% of benign tumors encountered during the neonatal period. Most often treated by surgical resection or sclerotherapy, phosphodiesterase inhibitors have recently emerged as a potential treatment modality for lymphatic malformations. Treatment with phosphodiesterase inhibitors may be particularly useful when patients are not candidates for surgical resection or sclerotherapy. We report a case of giant bilateral lymphatic malformations diagnosed prenatally and treated postnatally with sildenafil.