INTRODUCTION: This study was undertaken to assess whether 3-dimensional computed tomography (CT) can be used to evaluate the relationships between the mandibular muscles and craniofacial morphology in children with different underlying vertical facial patterns. METHODS: Twenty children (mean age, 11.9 +/- 1.6 years) underwent cranial CT examination. Three-dimensional CT images were reconstructed for the evaluation of the cross-sectional size, volume, and spatial orientation of the masseter, medial pterygoid, and lateral pterygoid muscles. These muscle factors were also assessed in relation to vertical and transverse craniofacial form. RESULTS: Positive correlations were found between the muscles' cross-sectional area and volume, and between muscle size and transverse facial width. Despite the limited sample size, differences were also found in the orientation of the masseter and medial pterygoid muscles in growing patients with different underlying vertical facial patterns. CONCLUSIONS: Three-dimensional CT can be used for the assessment of soft- and hard-tissue dentofacial forms. Clinicians should note the potential differences in muscle cross-sectional area, volume, and orientation in subjects with different underlying vertical facial patterns.