A 41-year-old male patient presented with dull left flank pain. A computed tomography (CT) showed a subdiaphragmatic retroperitoneal extra-adrenal mass. A magnetic resonance image demonstrated it was hypointense on T1 weighted and hyperintense on T2. Serum analyses for adrenal hormones revealed no abnormality. [I131]metaiodo-benzylguanidene scintigraphy showed no abnormal uptake. The patient underwent laparoscopic removal to manage the symptoms and to make a pathological diagnosis, which was an extralobar pulmonary sequestration. Another congenital lung malformation was not detected on chest CT scan. The symptom was relieved postoperatively.