Introduction: Right ventricular (RV) function assessed by cardiac magnetic resonance (CMR) is reported to more strongly predict outcome in patients with pulmonary arterial hypertension (PAH) than haemodynamics. RV strain by echocardiography is reported to be correlated with the mean pulmonary arterial pressure (mPAP) in patients with pulmonary hypertension (PH). Aims: This study aimed to investigate whether RV strain obtained with CMR, more objective than echocardiography, can be correlated with mPAP in patients with PH. Methods: We retrospectively analysed CMR data for 38 consecutive patients (mean age, 54.9±16.5 years; 79% women; World Health Organization functional class, I/II/III/IV=6/17/15/0) with PH, except Group 2, between 2015 and 2021. They underwent CMR and right heart catheterisation (RHC), where mPAP was 39±12 mmHg, cardiac index was 2.7±1.1 L/min/m2, and PVR was 7.9±4.8 Wood units. They consisted of Group 1 (PAH) in 27 patients, Group 3 in 3, and Group 4 in 8, according to the latest ESC/ERS guidelines. Results: In all the patients, CMR detected impaired RV ejection fraction (RVEF, 35.7±13.8%), with depressed RV free wall strain (RV-FS, -16.2±6.9%). Among CMR parameters, RV-FS showed the best correlation with mPAP measured by RHC (r=0.67, p<0.0001), compared to RVEF (r=-0.64, p<0.0001). Receiver operating characteristic analysis revealed that RV-FS of -13.7 and -14.1% could detect mPAP ?42 and ?30 mmHg (sensitivity 86 and 54%, specificity 91 and 88%, area under the curve 0.92 and 0.72, both p<0.05), respectively.Conclusions: These suggest that RV-FS may be useful for noninvasively assessing mPAP in patients with PH.