When treating patients with orthognathic surgery, there might be a risk of obstructive sleep apnoea (OSA) due to soft tissue changes in the upper airways, especially in patients treated with isolated mandibular setback or mandibular setback in combination with maxillary advancement. In the present study, we assessed respiratory function during sleep with home cardiorespiratory polygraphy in 62 patients who had not been previously been diagnosed with OSA at three times: prior to orthognathic surgery for aesthetic and functional indications, and then 3 months and 1 year after surgery. We evaluated surgical displacement based on measurements in three dimensions using pre- and post-operative computed tomography. There were only minor changes in the respiratory parameters such as the apnoea-hypopnoea index (AHI), the apnoea-hypopnoea index in the supine position (AHIsup), the oxygen saturation index (ODI) and the snore index. There was no significant correlation between surgical displacement and the AHI, AHIsup and ODI. There was a weak but significant correlation between vertical displacement of the anterior mandible and the snore index. Within the limitations of the present study, the risk for iatrogenic obstruction of the upper airways seems to be low in patients without OSA treated with orthognathic surgery.