Background: Right ventricular (RV) function is one of the most important determinants of outcome for patients with pulmonary hypertension (PH). Furthermore, mid-term RV reverse remodeling after treatment is also associated with long-term outcome as well as RV remodeling before treatment. However, baseline factors influencing mid-term RV reverse remodeling after treatment remains unclear. Methods: We studied 54 PH patients. RV function was calculated by averaging peak speckle-tracking longitudinal strain from RV free-wall (RV free-wall strain). Mid-term RV remodeling was assessed in terms of the RV area, which was traced planimetrically at the end-systole (RVESA). RV reverse remodeling was defined as a relative decrease in RVESA of at least 15% at 10.2 ± 9.4 months after treatment. Long-term follow-up was tracked for 5 years. Results: Adverse events occurred in 10 patients (19%). Mid-term RV reverse remodeling after treatment was observed in 37 patients (69%). Patients with mid-term RV reverse remodeling had more favorable long-term outcome than those without (log-lank p=0.01). Multivariate logistic regression analysis showed that RV relative wall thickness (RV-RWT), which was calculated from RV free-wall thickness/RV basal linear dimension at end-diastole, was the independent predictor of mid-term RV reverse remodeling (OR 1.403; 95% CI, 1.090-1.807; p=0.009). In addition, patients with RV-RWT≥0.21 experienced favorable long-term outcome than those without (log-rank p=0.03). Sequential Cox models show that a model based on symptom, hemodynamic parameters was improved by addition of RV free-wall strain (χ 2 =13.3; p=0.08), and was further improved by addition of RV-RWT (χ 2 =28.9; p<0.01). Conclusion: RV-RWT could predict mid-term RV reverse remodeling after treatment in PH patients, and was associated with long-term outcomes. Our findings may have clinical implications for better management of PH patients.