The purpose of the present study was to evaluate the accuracy and reliability of airway volume digital measurements of cone-beam computed tomography (CBCT) compared with the manual measurements of an airway model. An acrylic airway model was constructed and attached to a human dry skull in the natural position of the airway passage. The total and internal airway volumes, as well as the most constricted airway area, were measured manually on the model and on the CBCTs taken after the model was attached to the skull. The CBCT images were analysed using the Dolphin3D (Dolphin Imaging & Management solutions, Chatsworth, California, USA) software. Reliability and accuracy were assessed by using intraclass correlation and Student’s t-test. A P ≤ 0.05 was considered statistically significant. No significant statistical difference was found between the total, the internal airway volume, and the most constricted airway area measured on CBCTs compared with the manual measurements. The intra-examiner reliability was high for all measurements recorded from both methods (r ≥ 0.90). These results suggested that the three-dimensional CBCT digital measurements of the airway volume and the most constricted area of the airway are reliable and accurate. The use of CBCT imaging for the assessment of the airway can provide clinically useful information in orthodontics.