Excellent reviews have been written recently on both efficacy and equipment options of various types of continuous positive airway pressure (CPAP) systems (J Thorac Dis 7:1323-42, 2015), as well as technical descriptions of how different makes and models of PAP systems operate (Med Devices 8:425-37, 2015). However, there is little in the literature discussing fundamental aspects of CPAP such as alternative options for pressure selection, as well as how mask interface can impact successful patient treatment. Therefore, in this paper, although many of the commonly discussed aspects of CPAP will be addressed briefly, such as compliance issues, humidification, and pressure relief options, more effort is spent discussing little known (or discussed) topics such as predictive formulas for CPAP setting and how mask interface can effect treatment efficacy.