Abstract: Objective: To study the diagnosis and differential diagnosis values of CT and MRI in Grynfelt-Lesshaft's hernia. Methods: From August 2013 to December 2016,in our hospital, the data of clinical and imagings of 28 patients with Grynfelt-Lesshaft's hernia confirmed by operation or clinical were retrospectively analyzed. All patients underwent multi-slice spiral CT examination, and three of them also underwent MRI examination. Results: Of all the 28 patients, 20 were male, 8 were female, age: 44 to 80 years (average 69.04~3.5 years). Unilateral in 16 cases (right side in 12 cases, left side in 4 cases), bilateral in 12 cases. On the imagings of CT and MRI, the hernia located in the Grynfelt-Lesshaft triangular (superior lumbar triangular) region, which his boundaries were formed superiorly by the 1 lth or 12th thoracic rib, medially by the erector spinae muscle group, laterally by the internal oblique muscle. The floor of this triangle was formed by aponeurosis of the transversalis muscle, and the roof was formed by the latissimus dorsi muscle. CT or MRI showed oval or flask shaped mass of extraperitioneal fat with or without peritoneum and visceral contents protruded through the defecting fascia floor into lumbar triangle, and the size of the hernia contents was out of proportion with the hernia ring.Hernia ring in diameter ranged from 1.5 to 8.7cm, and the hernia sac size ranged from 1.6 cm- 1.3cm to 9.2cm-5.4 cm. Imagings of CT and MRI were easy to differentiate Grynfelt hernia from other lesions such as outborrd and posterior abdominal wall hernia, bulging or pseudohernia abdominal wall hernia, lipoma and other soft tissue tumors, hematoma and abscess. Conclusion: CT and MRI can clearly show the ring size of Grynfelt-Lesshaft's hernia hernia, the hernia contents and possible complications, the weak and defect degree of the abdominal wall muscles around. CT and MRI are helpful for diagnosis of Grynfelt-Lesshaft's hernia and differentiation from other diseases, and worthy of application.