Although lateral meningoceles have been described in the thorax, they have not been previously reported in the neck. We describe an infant who was born with a lateral meningocele in the cervical posterior triangle that was felt clinically to be cystic hygroma. Surgical excision was complicated by a cerebral spinal fluid fistula and subsequent meningitis. Problems that this patient presented and potential complications in management are discussed. Although the clinical manifestations of lateral meningoceles and extradural cysts are quite different, there are many anatomic similarities between these entities and other cervical masses that confuse diagnosis and nosology. Their differential diagnosis is reviewed.