Patients with chronic thromboembolism with pulmonary hypertension (CTEPH) often develop severe hypoxaemia after pulmonary thromboendarterectomy. There is reluctance to apply high positive end-expiratory pressure (PEEP) to those patients, whereas high PEEP is important for acute hypoxaemic respiratory failure due to alveolar collapse. Open lung approach (OLA) policy, a combination of recruitment manoeuvre and PEEP titration, may improve oxygenation and lung mechanics in acute hypoxaemic respiratory failure, but the effect of OLA on the outcome is unknown. We designed a case-matched, retrospective study to investigate whether OLA policy improved the outcome of postoperative patients with CTEPH. Among 113 postoperative patients with CTEPH, 40 were chosen before and after the introduction of an OLA policy to create 1:1 ratio of case-match according to gender, age and preoperative total pulmonary resistance index (conventional treatment group vs. OLA group). In the OLA group, recruitment manoeuvre was applied and then PEEP was titrated to maintain oxygenation every 12 hours. Gas exchange and duration of mechanical ventilation were compared between the groups. The OLA group showed higher PaO2/FiO2 ratio at 12 hours after the surgery than the conventional group (P = 0.0021). In the OLA group, duration of mechanical ventilation was shorter than the conventional treatment group (median, 23.5 hours vs. 43 hours, P = 0.0064). The OLA group showed lower cardiac index, higher pulmonary artery pressure and higher total pulmonary resistance index after the surgery than the conventional group. The introduction of the OLA policy may have shortened mechanical ventilation duration despite what appeared to be less favorable early postoperative hemodynamics in patients after the surgery for CTEPH.