Positive airway pressure (PAP) is the treatment of choice for patients with moderate-to-severe obstructive sleep apnea (OSA). Randomized controlled trials have demonstrated that PAP can effectively reduce the apnea-hypopnea index and improve subjective and objective sleepiness. Some studies have also demonstrated benefits in sleep quality and quality of life for both the patient and bed partner. Observational studies have shown a reduction in the risk of cardiovascular events in OSA patients treated with PAP compared to untreated patients. Since continuous PAP (CPAP) treatment of OSA was described, additional modes of pressure delivery have been developed (bilevel PAP, autoadjusting PAP, flexible PAP). While none of the variants of PAP improves adherence in unselected patients compared to CPAP, individual patients may respond to a change in pressure mode. Attended PAP titration remains the standard of practice for selecting a treatment pressure. However, use of autotitrating PAP devices in the unattended setting can provide an effective titration alternative with careful patient selection and review of titration results. More choices of mask interface are now available to improve comfort and intervene for mask or mouth leaks. However, despite the increase in PAP treatment options, lack of acceptance and inadequate adherence to PAP therapy remain the major causes of treatment failure. Some studies suggest that heated humidification can improve PAP adherence, especially in patients with nasal congestion or dryness. A systematic approach to PAP treatment including education, objective adherence monitoring, early intervention for side effects, and telephone and clinic support is essential to optimize adherence.