In the new WHO classification, odontogenic keratocyst is categorized as a benign odontogenic tumor under the name of keratocystic odontogenic tumor (KCOT). KCOT is a cystic lesion showing aggressive, infiltrative behavior and a tendency to recur. Multiple KCOT is usually one of the symptoms of nevoid basal cell carcinoma syndrome. The clinical and radiographic features of KCOT are similar to those of ameloblastoma. Pathologically, the lesion is lined by thin parakeratinized stratified squamous epithelium in which the surface shows a corrugated appearance. The basal lamina of the lining epithelium is flat, and the basal cells are cuboidal or columnar with a palisading pattern. The thin lining epithelium frequently separates from the underlying connective tissue, and is one of the causes of recurrence as well as daughter cyst and epithelial rests. A cystic lesion in which the whole lining epithelium shows orthokeratinization is referred to as orthokeratinized odontogenic cyst and should be separated from KCOT because recurrence is rare. Any cystic lesion lined by stratified squamous epithelium with features of both orthokeratinization and parakeratinization should be included under the category of KCOT.