Serous cystadenomas of the pancreas are slow growing tumors, rarely compressive and therefore rarely symptomatic. Morphologically typical serous cystadenomas can be safely followed up. We report here three atypical cases of serous cystadenomas compressing either biliary, pancreatic main ducts or splenic vascular pedicle. We analyze from the literature the frequency of these various compressions by different types of cystic pancreatic tumors of the pancreas. Because of the rarity of pancreatic ductal and vascular compressions by serous cystadenomas, the occurrence of such compressions should lead to surgical resection to rule out a pre-malignant or malignant cystic tumor. On the contrary, compression of bile ducts by serous cystadenomas appears as relatively frequent and is therefore less suggestive of potential malignancy. A simple bilio-enteric by-pass can be performed when lesions are morphologically typical of serous cystadenomas and confirmed by surgical biopsy.