The aim of this study is to understand the treatment patterns in patients with Pulmonary Arterial Hypertension (PAH) or Chronic Thromboembolic Pulmonary Hypertension (CTEPH) during a switch of treatment to Adempas in real-life clinical practice.

In addition, this study will describe patient demographics and reason for switching

Inclusion Criteria:

- Female and male adult patients diagnosed with PAH or inoperable/recurrent/persistent CTEPH who have been switched from a PH treatment (i.e. Endothelin Receptor Antagonist(ERAs), Phosphodiesterase-5 inhibitor(PDE5i) or Prostacyclin Analog (PCA) to Adempas

Exclusion Criteria:

• Patients participating in an investigational program with interventions outside of routine clinical practice
• Patients who have not switched their therapy from an Endothelin Receptor Antagonist (ERA) or Prostacyclin Analog (PCA) but received Adempas purely as an add-on therapy

Source population of the study are patients with Pulmonary arterial hypertension(PAH) and Chronic thromboembolic pulmonary hypertension (CTEPH). Patients with this rare condition are mostly diagnosed and managed at specialist centers. This includes initiation or any change of Pulmonary Hypertension (PH) therapy. The participation of these specialized centers in the study is going to ensure the representativeness of the study population. In order to reduce selection bias physicians will be asked to include all eligible patients.