A rare case of thoracoabdominal duplication is reported. Radiological workup including US, CT and MR provided the correct diagnosis. The US revealed the cystic nature of the lesions, whereas CT and MR showed their relationship with the diaphragm and each other. Coronal- and sagittal-plane MR images were helpful in demonstrating the extension of the lesions. The patient was discharged after an uneventful surgery and recovery. The histological evaluation revealed the cyst lined with single-layered columnar epithelium and the cyst wall contained submucosal mucous glands with underlying smooth muscle and also some mature chondroid elements with bronchogenic origin. Radiological findings and differential diagnosis are discussed.