We report the computed tomographic diagnosis of non strangulated obturator hernia. We treated 5cases of obturator hernia, in which 3 cases had ileocecalgia and thigh pain due to obturator hernia for many years and received CT examinations when occurred that pain. Retrospectively, any CT revealed non strangulated obturator hernia in 3 cases. We investigated any features of non strangulated obturator hernia from CT exam, and measured the interval of external obturator muscle and pectineal muscle on CT films of obturator hernia's patients and 20 healthy elderly women. On the result, the interval of external obturator muscle and pectineal muscle is average length of 9 mm in cases of non strangulated obturator hernia,24mm in cases of strangulated obturator hernia and 3.8mm in 20 healthy eldely women, which is shorter significantly than that of non strangulated obturator hernia. In the cases of non strangulated obturator hernia, CT revealed linear and nodular high density shadow in the space of external obturator muscle and pectineal muscle, but in the cases of normal women, nothing. We concluded that non strangulated obturator hernia is suspected by CT examination when the interval of external obturator muscle and pectineal muscle is larger than 10mm and linear and nodular high density shadow is appeared in the space of external obturator muscle and pectineal muscle.