The comparison between the pulmonary vascular tissues of lung transplant donors (control) and CTEPH patients showed that HIF‐1α expression increased in the pulmonary vascular tissues of CTEPH patients (p = 0.046), whereas eNOS expression decreased in the pulmonary vascular endothelium of CTEPH patients, although without a statistically significant difference (p = 0.216). This evidence concerns the gene NOS3 and chronic thromboembolic pulmonary hypertension.