Isolated obstruction of the splenic vein constitute 5-10% of all patients with portal hypertension. The evaluation of splenic vein patency is important in assessing inflammatory or neoplastic diseases of the pancreas. Accurate preoperative diagnosis is therefore essential to allow the correct choice of operative procedure. A case of isolated splenic vein obstruction with left-sided portal hypertension secondary to cystadenocarcinoma of the pancreas is reported in order to discuss criteria of preoperative diagnosis between benign and malignant cystic lesions of the pancreas.