The significance of duodenal diverticula is studied, in particular with respect to the supposed role of juxtapapillary diverticular in the development of biliary and/or pancreatic diseases. Duodenal diverticula were found in 72 cases with the help of duodenoscopy and ERCP, i.e. in altogether 1% of the patients investigated by upper GI endoscopy. On the basis of their observations and the data reported in the literature, the authors conclude that the pathological role played by juxtapapillary diverticula in the development of biliary and/or pancreatic diseases is by obstructing the pancreatic juice and bile flow. Stones are frequently found in the common bile duct in patients with juxtapapillary diverticula. At biliary surgery the observed diverticulum, which impedes biliary flow, must be taken into consideration, too. In such cases the aim of surgery is to guarantee free biliary flow, without which the operation cannot be considered successful.