Duodenal adenomas are relatively uncommon neoplasms in the general population. They are traditionally treated surgically but with a high injury and mortality rate. Endoscopic methods are increasingly being used for treatment of epithelial tumors of the duodenum. Despite an extensive use of the endoscopic submucosal dissection in esophagus, stomach and colon, the implementation of this treatment in duodenum is significantly less spread because of often arising complications. However this method significantly reduces the relapse rate associated with piecemeal endoscopic resection. In a clinical case study we show complication in a 72 year old patient after the resection of a duodenal adenoma using endoscopic submucosal dissection method. On the first day after the procedure necrosis occurs in place where the dissection was. The perforation zone which was situated on the wall opposite to major duodenal papilla and occupied the half of intestine circumference was removed by formation of duodenojejunum anastomosis. On the 12-th day after this emergency surgery the patient was released in satisfactory condition. The perforation rate after endoscopic submucosal dissection in duodenum reaches 50%. An endoscopic method can be used for treatment of neoplasms in duodenum but patient should be well informed of risks and complications after this manipulation. Therefore, surgeons and endoscopists should cooperate closely in case of complications.