Introduction and aimEndoscopic retrograde cholangiopancreatography (ERCP) is a complex procedure. Clinical guidelines assess competence in ERCP through a defined number of procedures, but multiple factors are involved. Our aim was to analyze the morphology of the papilla of Vater as an independent factor in selective common bile duct cannulation during resident training. Material and methodsPatients that underwent ERCP were studied consecutively. All ERCPs were begun by a resident in training. The type of papilla was classified according to Haraldsson, including those with previous sphincterotomy. Cannulation difficulty and success and their relation to the type of papilla were documented. The analysis was divided into three 4-month periods. ResultsOf the 429 patients, cannulation was difficult in 101 (23.5%). The residents achieved selective cannulation of the common bile duct in 276 (64.3%) and the cannulation success rate at the end of their training was 81.7%. Cannulation was performed with the least difficulty in papillae with previous sphincterotomy (2.8%), unlike the type 4 papilla, which was difficult to cannulate in 50% of the cases. The lowest overall cannulation success was in the type 2 papilla (81.8%). ConclusiónPapilla type can influence cannulation success, but it is not the only related factor. Patients that underwent previous sphincterotomy appear to be the cases in whom ERCP training can be started.