BACKGROUND: Coronoid process hypertrophy can be associated with a variety of congenital or acquired anomalies. There is, however, no consensus on a quantitative or objective measure to define coronoid hypertrophy. Here, the authors describe a novel analytical technique using three-dimensional computed tomographic data to accurately and reproducibly assess coronoid size and diagnose coronoid:condyle disproportion. METHODS: A total of 24 patients were analyzed using three-dimensional medial axis analysis, eight with of unilateral coronoid hypertrophy, four with of bilateral coronoid hypertrophy, and 12 age-matched normal control patients. RESULTS: Measurement of normal subjects (n = 12) demonstrated a coronoid:condyle volumetric ratio less than or equal to 0.5. Analysis of patients with coronoid hypertrophy demonstrated that a coronoid:condyle volumetric ratio greater than or equal to 1.0 was consistent with marked coronoid:condylar disproportion and a ratio between 0.5 and 1.0 was indicative of modest disproportion. Surface area ratios comparing coronoid with condyle were also elevated (ratio, ≥0.5) in patients with coronoid hypertrophy. CONCLUSIONS: Quantitative assessment of coronoid size using three-dimensional volume and surface area analysis of computed tomographic data may be helpful to the clinician in diagnosing coronoid hypertrophy and in guiding treatment. It may also serve a role in monitoring the temporal evolution of coronoid hypertrophy in early cases that have not yet resulted in trismus or decreased interincisal opening. CLINICAL QUESTION/LEVEL OF EVIDENCE: Diagnostic, IV.