Tumors of the small intestine are rare as compared to malignant tumors of the pancreas. Here we report on the case of a 61-year-old man suffering from chronic pancreatitis presenting with a lesion projecting into the pancreatic head shown by both computed tomography and transabdominal ultrasound. Pancreatic cancer was suspected, but endoscopic ultrasound revealed this lesion to be situated in the submucosal layer of the duodenal wall. Surgery was performed since biopsy of this lesion was not diagnostic and a malignant leiomyosarcoma could therefore not be excluded. Limited surgery comprised resection of the duodenal lesion, whereas based on computed tomography alone, exploration of the pancreas would have been performed. Thus, in the present case endoscopic ultrasound leads to a more appropriate, less invasive therapeutic measure.