This study was performed to evaluate the long-term impact of maxillomandibular advancement (MMA) surgery on the apnoea–hypopnoea index (AHI) and quality of life (QoL) in patients with obstructive sleep apnoea syndrome (OSAS). The medical files of 12 OSAS patients who underwent MMA by one surgeon between 1995 and 1999 were reviewed retrospectively. Patients received a clinical assessment, polysomnography, and QoL questionnaires as part of routine care preoperatively (n=12), within 2 years postoperative (n=12), and again in 2016 (n=9). A successful surgical outcome was defined as an AHI decrease of >50% with <20 events/h. Of the 66.7% (8/12) of patients who were initially cured, 66.7% (4/6) remained stable at a median follow-up of 19 years. Only the two patients with the highest AHI showed abnormal Epworth Sleepiness Scale scores. After convalescence, most patients reported stable symptomatic improvement. Aesthetic changes were found acceptable and all but one patient stated that they would undergo the surgery again. It is concluded that MMA is a safe and effective procedure. Ageing and weight gain might counterbalance the positive effects of surgery in the long term. It is therefore suggested that re-evaluation every 5 years should be scheduled, since a spontaneous AHI increase over time does not seem to be reflected by symptomatic changes.