Introduction: The objective of this study was to investigate whether a reduction of obstructive sleep apnoea (OSA) severity is associated with significant airway and craniofacial changes with mandibular advancement device (MAD) in Chinese subjects. Materials and Methods: A total of 14 Chinese subjects (8 males, 6 females) diagnosed with OSA by overnight polysomnography (PSG), were fitted with the MAD. The mean ± standard deviation baseline apnoea-hypopnoea index (AHI) was 38.4 ± 17.2 and minimum arterial oxygen saturation (SaO2) was 75.5 ± 11.1%. The second lateral cephalogram was taken (wearing the MAD) after the second PSG. The second PSG was indicated when symptoms have improved as shown by the Epworth Sleepiness Score and sleep questionnaire after wearing the MAD for 1 month. Comparison of cephalometric variables was done to evaluate the effects of the MAD on the upper airway and anatomical variables. Pre-treatment versus post-treatment variables were compared using Wilcoxon signedrank test to determine the statistical significance at the 5% levels. The changes in airway variables were correlated with the changes in AHI using the Spearman correlation test. Results: At the second polysomnogram, AHI was significantly reduced to 10.9 ± 14.7. Minimum SaO2 was significantly increased to 86 ± 8.4%. Mean airway dimension was significantly increased at the nasopharyngeal area from 22.7 ± 3.0 mm to 24.8 ± 2.1 mm. The distance of the hyoid bone to the mandibular plane was significantly reduced with the MAD from a mean of 21.2 ± 5.7 mm to 13.9 ± 7.0 mm (P <0.05). This reduction of the distance of the hyoid bone to the mandibular plane was significantly correlated with the reduction in the AHI. Conclusion: An increase in the nasopharyngeal airway and reduction of the distance of the hyoid bone to the mandibular plane was observed for this sample of Chinese OSA subjects. This study forms the baseline for future studies on the effects of MAD on the airway and craniofacial structures in a larger sample. Key words: Lateral cephalogram, Mandibular advancement splint, Mandibular advancement device, Obstructive sleep apnoea, Polysomnogram