Bilateral coronoid process hyperplasia is a rare condition defined as an abnormal elongation of the mandibular coronoid process, formed of histologically normal bone. Coronoid process hyperplasia usually develops progressively, and the clinical symptoms are often similar to those of temporomandibular joint disorders (TMD). Therefore, it is often misdiagnosed as TMD initially. From 2013 to 2016, six patients were referred to our maxillofacial surgery unit by their dentist, to evaluate mouth opening with suspected TMJ disorder. Average age was 30 years No hypertrophy of the masseter muscles was found and the patient had no history of pain and/or dysfunction of the temporomandibular joint. Average maximal incisal opening was 16.3 mm. (Rance 13-20 mm). At the end of surgery the average mouth opening achieved was of 40.3 mm. After 6 months from surgery an average mouth opening of 41 mm was obtained, with no recidivism in the coronoid process growth or decrease in the mouth opening. The only successful treatment to restore the mouth opening caused by coronoid process hyperplasia is surgical correction of coronoid-malar interference by coronoidectomy or coronoidotomy. Commencement of physiotherapy is recommended to begin between three days and one week after surgery. We also recommend the use of the TeraBite®, a simple manual physiotherapy device.