Abstract: Objective To retrospectively compare the difference of the effects of pulmonary thromboendarterectomy (PTE) between distal and proximal types of chronic thromboembolic pulmonary hypertension (CTEPH). Methods The data of 70 patients (including 44 male patients and 26 female patients, the average age was 46.2 years old, ranging from 17 to 72) with CTEPH having undergone PTE from March 2002 to March 2009 in Anzhen Hospital were retrospectively reviewed. We classified them into two different groups which were the proximal CTEPH group (n=51) and the distal CTEPH group (n=19) according to the pathological classification of the CTEPH. Clinical data, hemodynamics blood gas analysis and so on of both groups were compared. Results There was no perioperative deaths in both groups. Compared with the proximal group, cardiopulmonary bypass time [CM(159mm](189.5±41.5 min vs.155.5±39.5 min,P=0.003), aorta cross clamp time (91.3±27.8 min vs.67.2±27.8 min,P=0.002) and DHCA time (41.7±14.6 min vs.25.7±11.6 min,P=0.000) were significantly longer in the distal group. The incidence of residual pulmonary hypertension in the distal group was significantly higher than that in the proximal group (42.1% vs.13.7%,P=0.013), while the incidence of pulmonary reperfusion injury postoperatively in the proximal group was significantly higher than that in the distal group (41.2% vs.10.5%, P=0.021). SwanGanz catheterization and blood gas index were obviously improved in both groups. However, the pulmonary artery systolic pressure (PASP, 67.8±21.3 mm Hg vs.45.5±17.4 mm Hg,P=0.000) and the pulmonary vascular resistance ［PVR, 52.8±32.1 kPa/(L·s) vs.37.9±20.7 kPa/(L·s),P=0.024］ in the distal group were significantly higher than those in the proximal group and the partial pressure of oxygen in arterial blood of the distal group was significantly lower than that of the proximal group (76.7±8.7 mm Hg vs.88.8±9.3 mm Hg,P=0.000). After operation, 70 patients were followed up with no deaths during the followup period. The time of the followup ranged from 2 to 81 months (32.7±19.6 months) with a cumulative followup of 191.8 patientyears. Three months after operation, 47 patients were examined by pulmonary artery computer tomography angiogram (PACTA) and isotope perfusion/ventilation scan, which showed that the residual occlusive pulmonary artery segment in the proximal group was significantly fewer than that in the distal group (isotope perfusion/ventilation scan: 2.2±11 segments vs. 4.7±2.1 segments, P=0.000; PACTA: 3.5±1.4 segments vs. 4.9±2.0 segments,P=0.009). The New York Heart Association (NYHA) functional class and 6 minute walk distance (6MWD) in the proximal group were significantly better than those in the distal group (1.7±0.5 class vs 2.3±0.4 class; 479.2±51.2 m vs. 438.6±39.5 m, P=0.003). Venous thrombosis in double lower limbs reoccurred in two patients. According to KaplanMeier actuarial curve, the freedom from reembolism at 3 years was 96.7%±2.8%. Bleeding complications occurred in three patients. The linear Bleeding rate related to anticoagulation was 2.47% patientyears. Conclusion Although the early and midlong term survival rate of PTE procedure to treat both proximal and distal types of CTEPH is agreeable, the recovery of the PASP, PVR and 6MWD, and blood gases in patients with proximal type of CTEPH are significantly better than those in patients with distal type of CTEPH. On one hand, anticoagulation can singularly provide enough protection to patients with proximal type of CTEPH, but on the other hand, diuretics and pulmonary hypertension alleviation drug should be added to the treatment regimen for patients with distal type of CTEPH after the procedure of PTE.