Coronoid hyperplasia is a rare condition which is macroscopically characterized by an increase in the dimensions of the coronoid process resulting from an abnormal bony elongation of histologically normal bone. Unilateral cases are more frequent than bilateral ones and can recognize a number of etiological factors, such as exostoses, osteochondroma, traumatic events, inflammatory reactions, neoplasia and manifestations secondary to other pathologies. Etiopathogenesis of bilateral forms has not yet been clarified: in the literature hints to both developmental and endocrine abnormalities are present, and a familiar pattern of inheritance has been evidenced. The poor specificity of signs and symptoms associated with coronoid hyperplasia, which are similar to those of other more frequent forms of temporomandibular disorders, present some problems of differential diagnosis. An accurate assessment must be based on a clinical and anamnestical approach aiming at the identification of pathognomonic clinical symptoms. Considering its limits (such as the possible presence of artefacts and image distortions), orthopantomography has a poor diagnostic usefulness. In this case, magnetic resonance (MR) allowed to evaluate disk-condyle relationship, but it could be also useful to evaluate post-operative complications. In the case of coronoid hyperplasia, the computed tomography (CT) is fundamental for a correct differential diagnosis. CT also allows surgical planning due to its accuracy to detect coronoid process volume and morphology. The present case report is an example of the need for a correct differential diagnosis between the different types of temporomandibular disorders, and it also lends support to the importance of requesting modern imaging techniques during the diagnostic process of the rare or complex cases.