OBJECTIVE: Resistant hypertension (RH) may be associated with Obstructive Sleep Apnea (OSA), determining a remarkable increase in cardiovascular risk. The aim of the study was to assess the effect of six months with continuous positive airway pressure (CPAP) treatment on blood pressure (BP) values, cardiovascular risk markers, and exercise tolerance in patients with RH and OSA. PATIENTS AND METHODS: Twenty-four patients with RH and OSA were recruited and 24-hour ambulatory BP, intima-media thickness (IMT), flow mediated dilation (FMD), renal resistive index (RRI), and endurance cardiopulmonary exercise testing (CPET) were obtained at enrollment and after 6-month treatment. RESULTS: Significant reduction in clinic systolic and diastolic BP, IMT, and RRI (p = 0.003, p = 0.009, p = 0.020, p = 0.04, respectively) and increase in the left ventricular ejection fraction (p = 0.035) were observed after a 6-month therapy with CPAP. Moreover, improvement in all polysomnographic parameters (number of apneas/hypopneas per hour (p < 0.001), number of episodes of night-time hemoglobin desaturation (ODI) (p = 0.010), an improvement in Epworth Sleepiness Scale (p < 0.001), as well as in endurance time during constant workload CPET (p = 0.017) were observed too. CONCLUSIONS: CPAP treatment for six months reduces BP and improves cardiovascular risk and exercise tolerance in patients with RH and OSA. An extended cardiovascular assessment, including exercise testing, might be helpful in this population, given the possible reversibility of some endothelial dysfunction and atherosclerotic markers with CPAP treatment, as reported in our study.