Noninvasive ventilation (NIV) in patients with respiratory failure due to primary lung disease may sometimes require invasive assessment of the pulmonary circulation. The indication for right heart catheterization (RHC) using the Swan–Ganz catheter in these patients is the suspicion of pulmonary hypertension (PH) in the course of lung diseases, as well as other types of pulmonary hypertension, including chronic thromboembolic pulmonary hypertension. This type of PH is suspected in patients who additionally have had an incident of deep vein thrombosis/pulmonary embolism or have mismatch disorders documented in ventilation and perfusion scintigraphy. Another independent indication for RHC in a mechanically ventilated patient is the qualification for lung transplantation (LTx) or heart transplantation (HTx). Patients ventilated with NIV belong to a specific and special group of patients requiring an individual diagnostic approach and individual clinical decisions. Due to the features of the disease, both pulmonary hypertension and the coincidence of PH with NIV, right heart catheterization procedures in a patient with NIV are rarely performed. This chapter describes patients ventilated with NIV undergoing RHC, as well as the clinical implications of the RHC results.