Chronic thromboembolic pulmonary disease (CTEPD) is defined by chronic organized thrombi in the pulmonary circulation without or with pulmonary hypertension (CTEPH). The current definition of CTEPH has adopted lower mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) thresholds. Our aim was to identify its impact on the characterization of patients with CTEPD. All consecutive CTEPD patients referred for cardiopulmonary exercise testing (CPET) in a PH center were divided into four groups based on pulmonary haemodynamics. Group A: mPAP≤20 mmHg, Group B: mPAP>20 mmHg with PVR>2 and ≤3 WU, Group C: mPAP>20 mmHg with PVR>3 WU, Group D: mPAP>20 mmHg with PVR<2 WU (''unclassified''). We compared CPET, CT pulmonary angiography, and MRI data across the groups. There was mild aerobic capacity impairment, mild/moderate ventilatory inefficiency, and no significant cardiac limitation on CPET in all groups. However, patients in Groups A and D had better ventilatory efficiency and less oxygen desaturation on exercise due to lower dead-space ventilation. There was no difference in chronic pulmonary emboli burden and distribution, or resting RV function between the groups. Seventeen patients were reclassified as having ''CTEPH'' based on the current definition. No functional deterioration was noted within a median period of 13 months on repeat CPET. CTEPD patients with similar clot burden and RV function without or with mild/moderate PH displayed a similar pattern of cardiopulmonary limitation, except for ventilatory efficiency. The current definition for CTEPH may lead to reclassification of CTEPH in a considerable number of patients.