Introduction: Right heart catheterization (RHC) is used to diagnose and classify pulmonary hypertension (PH). Because RHC is invasive, there is growing interest in non-invasive PH evaluation techniques, such as cardiac magnetic resonance (CMR). Hypothesis: CMR-derived fibrosis indices [native T1 (NT1) and extracellular volume (ECV)] differ between pre-capillary PH (PRE-PH), post-capillary PH (POST-PH) and controls. Methods: RHC-defined PH patients and healthy controls (N=25, age=52+/-13 years) underwent CMR. A cardiologist classified patients into PRE-PH (N=29, age=55+/-8 years) and POST-PH (N=19, age=66+/-13 years) based on RHC measurements and clinical history. T1 maps of the left ventricle were acquired using a Modified Look-Locker Inversion Recovery sequence before and after administration of gadolinium contrast. T1 maps were manually segmented using the AHA 16 segment model to obtain segmental native and post-contrast T1. Segmental ECV was calculated using NT1, post-contrast T1, and hematocrit. Global ECV and NT1 were calculated by averaging all segments. Results: PRE-PH had higher NT1 than POST-PH in segments 8 (1077+/-39 vs 1046+/-36 ms, p=.01), 9 (1082+/-47 vs 1051+/-44 ms, p=.03), and 14 (1080+/-74 vs 1028+/-53 ms, p=.01). Global ECV and NT1 were higher in PRE-PH (31+/-4% and 1056+/-36 ms) than controls (28+/-4% and 1013+/-29 ms) (p=.017 and p=.000, respectively). Conclusions: NT1 was different between PRE-PH and POST-PH in mid- and apical-septal segments, however segmental ECV and global measures were not. NT1 may reflect more than just ECV expansion, providing additional insight into the myocardium. Regional NT1 may complement RHC for classifying PH.