Chronic thromboembolic pulmonary hypertension (CTEPH) is the most severe long-term consequence of acute pulmonary embolism (PE) and is frequently diagnosed at an advanced stage. It is characterized by thromboembolic pulmonary vascular lesions, persisting despite adequate anticoagulant therapy and leading to increased pulmonary artery pressures and secondary microvascular vasculopathy. Initially, the right ventricle will adapt to the increased pulmonary pressures by increasing its wall thickness (hypertrophy). However, as the disease advances and pulmonary pressures increase even more, the right ventricle will dilate and eventually, if left untreated, right ventricular failure will occur. Pulmonary endarterectomy (PEA) is the gold standard treatment for patients with CTEPH, in which the obstructive thromboembolic lesions are surgically removed. PEA results in significant hemodynamic and functional improvement. However, some patients will have residual pulmonary hypertension (PH) or exercise intolerance after PEA. To investigate the mechanism of residual pulmonary hypertension and exercise intolerance after PEA, it is important to understand CTEPH from both the perspective of the pulmonary arteries and the right ventricle. In this thesis we aimed to improve our understanding of CTEPH, from early detection of the disease to long-term management after treatment, in order to contribute to earlier recognition of CTEPH and a better patient selection for PEA. To accomplish our aim we investigated the manifestations of CTEPH in two locations: in the pulmonary arteries and the right ventricle.