Objective To evaluate the usefulness of MRCP in the diagnosis of Lemmel's syndrome.Methods 49 patients with periampullary diverliculum(PAD) were examined by MRCP.The clinical manifestations and imaging signs were analyzed,the detecting rate of PAD by MRCP,the anatomic relationship between pancreaticobiliary tract system and PAD were evaluated.Results Of 49 patients,47 PAD were showed on MRCP,in which 34 PAD located above the papilla,7 located below papilla,4 located in the neck edge of diverticula,and 2 were intradiverticular papilla.Conclusion MRCP as a newly developed and noninvasive imaging technique can improve the diagnosis of Lemmel's syndrome and will play an important role in the future.