Neuroenteric cysts are rare congenital anonalies, presenting in infancy or childhood. Only a few cases of posterior mediastinal neuroenteric cysts have been reported. A 12-year-old girl presented to our hospital with a neglected mildly painful cyst in the posterior mediastinum and retroperitoneum. Magnetic resonance imaging revelealed scoliosis of the thoracic spine, hemivertebrae T6 - 7, and a large hyperintense (on T2-weighted images) cystic lesion in the posterior mediastinum. The lesion had no intraspinal communication, but extended into the abdomen between the liver and kidney. Despite the long history and spatial extent of the lesion, it was excised uneventfully through a right thoracotomy. Microscopy of the cyst wall revealed partially disrupted cuboidal epithelium, muscle fibres, inflammatory cells, and, bony and cartilaginous elements. Enterogenous duplication cysts of foregut origin with vertebral anomalies are referred to as neuroenteric cysts. This is a probably only the second reported case of thoraco-abdominal neurogenic cyst originating in the posterior mediastinum.