Introduction: Periampullary diverticula (PD) is caused by extraluminal pouching of duodenal mucosa. Using a very common endoscopic procedure to diagnose or treat gastrointestinal disorders, we encountered duodenal diverticulum. Materials and methods: This is a retrospective, single-center study. Three thousand and sixteen patients on whom endoscopic retrograde cholangiopancreatography (ERCP) was performed at Ankara University Medical School, Department of Gastroenterology, from June 2009 to June 2014 were included to the study. Results: Hundred and thirty patients (males 65, females 65) among the 3,016 had PD. Two hundred and sixty patients without diverticulum were randomly chosen from the 3,016 patients, as a control group [121 (47%) females, 139 (53%) males]. There was no statistical difference between the two groups. The mean age of the patients with PD was 69.9 years, while the mean age was 62.3 years for patients without PD (p < 0.001). Incidence for PD was 4.6%. The papilla of Vater was located in the inter-diverticular area (Type 1) in 9 patients (8.3%), at the edge of the diverticulum (Type 2) in 31 patients (28.4%), and at a distance of 2 to 3 cm from the papilla (Type 3) in 69 patients (63.3%). Discussion: Although numerically more common bile duct stones occurred in patients with PD compared to those without PD, there was no statistical difference between the two groups. The rate of pancreatobiliary carcinomas was higher in patients without diverticulum. Cannulation was successful in both groups at the rate of 97.6 and 92% respectively, but cannulation failed more often in patients without PD. Duodenal perforation occurred in one patient with PD. Bleeding after sphincterotomy occurred in two patients without PD.