Coronoid process hyperplasia (CPH) is a rare condition characterized by the increase in the size of the coronoid process, mainly occurring in the second decades of human life. To provide a reference for the diagnosis and treatment of this disease, we reported the clinical manifestations of two cases, X-ray examination, treatment, and prognosis with mandibular movement and restricted mouth opening (RMO) caused by bilateral CPH. The opening degree of the two cases described in the article increased to almost 40 mm immediately after the elongated coronoid process was surgically removed and a case was maintained normal after 2 months. In another case, CPH recurred after 2 years of follow-up. The etiology of CPH is still unclear, which is associated with various factors. RMO caused by CPH is extremely rare in clinical practice, and it is easy for patients to get confused and be misdiagnosed. It should be diagnosed using comprehensive methods of clinical studies and imaging modalities. Currently, surgical coronoidectomy is an accepted treatment of CPH. Long-term effective opening training is crucial in maintaining its therapeutic effect.
