Objective: To evaluate the mandibular dental, alveolar, and skeletal transversal widths in patients affected by unilateral (UCLP) and bilateral (BCLP) cleft lip and palate and to compare the findings with a well-matched normal occlusion sample using cone beam computed tomography images. Materials and Methods: The study sample consisted of 75 patients divided into three groups: the UCLP (29 patients; mean age: 15.40 6 3.22 years), BCLP (18 patients; mean age: 15.54 6 3.72 years), and normal occlusion (28 patients; mean age: 15.82 6 2.11 years) groups. Mandibular dental (intercanine and -molar), alveolar (intercanine and -molar), and skeletal (bigonial width) transversal measurements were performed three-dimensionally and analyzed using the one-way variance analysis and post hoc Tukey tests. Results: Patients affected by UCLP and BCLP had statistically significantly lower intercanine alveolar widths (P , .05 and P , .001, respectively) and larger intermolar (P , .001 and P , .05, respectively) and intermolar alveolar widths (P , .001) compared with the normal occlusion group. Furthermore, the patients affected by UCLP and BCLP had similar mandibular dental, alveolar, and skeletal transversal widths (P . .05). Conclusion: The UCLP and BCLP groups showed statistically significantly smaller values for intercanine alveolar widths and larger values for intermolar dental and alveolar widths compared with the normal occlusion group. This shows the importance of using individualized archwires according to the pretreatment arch widths of the patients affected by UCLP and/or BCLP. (Angle Orthod. 2015;85:611-615.)