BACKGROUND The definitive treatment for chronic thromboembolic pulmonary hypertension (CTEPH) is pulmonary endarterectomy (PEA), which has good long-term outcomes. However, after surgery, a quarter of the patients still have residual pulmonary hypertension (RPH). In pulmonary hemodynamics, there are no unified criteria for RPH, even though the level may affect long-term survival. METHODS Between March 1997 and December 2021, 253 CTEPH patients were treated at our center with PEA. Patients were evaluated retrospectively and classified into early (1997-2014) and late (2015-2021) groups. The clinical characteristics and perioperative outcomes of the two groups were compared, and risk factor analysis for RPH and long-term survival for all cases was performed. RESULTS There was no statistically significant difference in demographics between the two groups. However, the Early Group had a significantly higher rate of perioperative death (9.8% vs. 1.2%, p = .001), RPH (48.8% vs. 14.0%, p < .001), and reperfusion pulmonary edema (18.3% vs. 2.9%, p < .001). The median follow-up time was 66.0 months, and overall survival rates at 5, 10, 15, and 18 years after PEA were 91.2%, 83.9%, 64.5%, and 46.0%, respectively. Age and postoperative systolic pulmonary artery pressure (sPAP) were independently related to long-term outcomes in the multivariate Cox analyses. Patients with postoperative sPAP less than 46 mm Hg had a higher chance of survival. CONCLUSIONS PEA improved CTEPH hemodynamics immediately and had a positive effect on long-term survival. Patients with postoperative sPAP ≥ 46 mm Hg indicate clinically significant RPH and have a lower long-term survival rate.