BACKGROUND : Cardiac magnetic resonance (CMR) imaging has gained importance in pulmonary hypertension (PH) and studies have demonstrated its use as a surrogate marker and in following treatment of these patients. The pathophysiology of PH differs between pulmonary arterial hypertension (PAH, group 1) and chronic thromboembolic PH (CTEPH, group 4). OBJECTIVE : The present study tested the hypothesis that PAH and CTEPH display different characteristics on CMR imaging. METHODS : 46 patients were evaluated for pulmonary vascular disease in the French National Reference Center for PH (23 PAH and 23 CTEPH matched for age and gender). All patients had the right heart catheterization (RHC) and CMR imaging performed within 48h. CMR imaging was performed on a 1.5 T scanner. RESULTS : PAH and CTEPH had similar body surface area and similar invasive hemodynamics, including mean pulmonary arterial pressure, cardiac index, pulmonary vascular resistance and right atrial pressure. PAH and CTEPH had similar CMR data. Right ventricular (RV) morphology and function and pulmonary artery (PA) data were also similar. CONCLUSIONS : Age- and sex-matched PAH and CTEPH patients displayed similar values of the CMR indices of RV and PA morphology and function, suggesting that the RV-PA responses are similar in both groups, mostly related to the overall increase in after load.