We recently experienced two cases of diaphragmatic hernia accompanied by no gastrointestinal gas, which could be preoperatively diagnosed by MRI. One was Bochdalek hernia, and the other was Morgagni hernia. In both cases, it was difficult to diagnose, because of homogenous shadows on chest X-ray films. MR imaging showed that each mass was continuous with the subphrenic tissue. As a result of operation, prolapse organs were the retroperitoneal fat tissue and greater omentum. It is important for decision-making of therapeutic methods and proper approach for operation to establish the definitive diagnosis preoperatively. MRI has an advantage over angiography and pneumoperitoneum in having lesser invasion, and its combined use with CT is recommended when this disease is suspected.