Among patients with sleep apnea the reported prevalence of precapillary pulmonary hypertension (PH) has varied largely, depending on patient selection, disease definition, and associated conditions, in particular chronic pulmonary disease. However, in the absence of comorbidities, PH seems to be rare in patients with sleep apnea. Conversely, sleep-related breathing disorders have been commonly found in patients with PH and they have been associated with an impaired quality of life. Since sleep-related breathing disorders may affect the pulmonary circulation and vice versa, patients with sleep-related breathing disorders should be evaluated for risk factors, symptoms and clinical signs of PH and right ventricular heart failure and patients with PH should be evaluated for sleep apnea. Therapeutic options for patients with sleep apnea and PH may include supplemental oxygen, drugs and positive pressure ventilation. Both nocturnal oxygen administration and acetazolamide have been shown to improve sleep apnea in patients with PH. In addition, oxygen therapy also improved exercise performance. Further studies are needed to corroborate the efficacy of these and other treatments.