Perhaps due to the increasing use of sensitive cross-sectional imaging of the abdomen, cystic lesions of the pancreas are being increasingly recognized. In many such cases, biopsy or resection reveals a multilocular cyst lined by columnar mucinous epithelium. Over the past two to three decades, there have been many advances in our understanding of the clinical, pathological, and molecular features of cystic mucin-producing pancreatic neoplasms, most of which are now broadly classified as either mucinous cystic neoplasms (MCNs) or intraductal papillary mucinous neoplasms (IPMNs). Although both share certain histological features and both are regarded to represent preinvasive neoplasms with the potential to progress to invasive carcinoma, there are many significant differences in their pathology and clinical management. The purpose of this review is to highlight the clinical and pathological characteristics of MCNs and IPMNs, with an emphasis of the features that distinguish them and allow proper pathological subclassification.