Odontogenic keratocyst is a cystic lesion characterized by a high rate of recurrence. This report describes a rare case of ciliated epithelium-lined odontogenic keratocyst in the maxilla of a 27-year-old female. Panoramic radiography showed a lytic lesion on the right maxilla associated with an impacted molar tooth. Computerized tomography image revealed the involvement of the lesion with the right maxillary sinus, destroying the sinus floor. Histopathologically, the typical keratinized epithelial-lined cyst of odontogenic keratocyst abruptly changed into a ciliated epithelium, suggesting the fusion of both these epithelia rather a metaplastic transformation. The biological behaviour of odontogenic keratocysts is discussed.