Objectives: Untreated obstructive sleep apnea-hypopnea syndrome (OSAHS) is associated with excessive daytime sleepiness, increased risk of cardiovascular (CV) disease, and road traffic accidents (RTAs), which impact survival and health-related quality of life. This study, funded by the French National Authority for Health (HAS), aimed to assess the cost-effectiveness of different treatments (i.e., continuous positive airway pressure [CPAP], dental devices, lifestyle advice, and no treatment) in patients with mild-to-moderate OSAHS in France. Methods: A Markov model was developed to simulate the progression of two cohorts, stratified by CV risk, over a lifetime horizon. Daytime sleepiness and RTAs were taken into account for all patients while CV events were only considered for patients with high CV risk. Results: For patients with low CV risk, incremental cost-effectiveness ratio (ICER) of dental devices versus no treatment varied between 32,976 EUR (moderate OSAHS) and 45,579 EUR (mild OSAHS) per quality-adjusted life-year (QALY), and CPAP versus dental devices, above 256,000 EUR/QALY. For patients with high CV risk, CPAP was associated with a gain of 0.62 QALY compared with no treatment, resulting in an ICER of 10,128 EUR/QALY. Conclusion: The analysis suggests that it is efficient to treat all OSAHS patients with high CV risk with CPAP and that dental devices are more efficient than CPAP for mild-to-moderate OSAHS with low CV risk. However, out-of-pocket costs are currently much higher for dental devices than for CPAP (i.e., 3,326 EUR versus 2,430 EUR) as orthodontic treatment is mainly non-refundable in France.