The odontogenic keratocyst(OKC) was used of term and described some of clinical, radiological and microscopic features by Philipsen 1956. The microscopic finding of OKC is characterized by the production of keratin, Which sometimes fills the lumen and thinning of epithelium of cyst. The most clinical importance of OKC is its extraordinary recurrence rate owing to the incomplete removal of the cyst wall. The final diagnosis of OKC should be evaluated by histologic findings and follow-up of any case of OKC with annual roentgenograms and clinical evaluations is essential for at least five years after surgery. This article is report of 2 cases of large OKC involved both molar portion and symphysis of mandible with facial asymmetry, severe bone destruction and paresthesia of lower lip on clinically, roentgenographically. By the postoperative findings the patients showed normal regeneration of bone defect area without recurrence signs by panorama films after surgery.