Morgagni, in 1760, 1st. described the findings of substernal herniation of abdominal contents into the thoracic cavity, based upon 25 postmortem dissections. Herniation through the foramen of Morgagni is the rarest occurrence of the congenital diaphragmatic hernias and is usually a few symptoms. With the increasing use of routine chest roentgenogram & the need to exclude the possibility of a mediastinal neoplasm, most such cases are brought to the attention of a surgeon. We had experienced 2 cases of Morgagni hernia, which one caused a simple mechanical intestinal obstruction & diagnosed as acute appendicitis with perforation & another one was diagnosed as mediastinal lipoma on routine chest X-ray film at arrival due to traffic accident. We had performed left paramedian abdominal incision as misdiagnosis of acute appendicitis with perforation and repair of the defect and returned transverse colon & stomach into abdominal cavity in one patient. And in another patient, we preferred to approach through right thoracotomy incision and then left upper paramedian abdominal incision and returned the omentum into the abdominal cavity. The post-operative courses were in uneventful and we report these cases and review and discuss the literatures.[KTCS 1983;2:221-225]