Chronic thromboembolic pulmonary hypertension (CTEPH) is a potentially fatal complication of pulmonary embolism (PE). Organized thrombus in the pulmonary artery causes a chronic obstruction, leading to a vascular system remodeling, an increase of pulmonary vascular resistance and a chronic pulmonary hypertension. Epidemiology is mostly unknown due to the difficult diagnostic process that often leads to a late diagnosis: findings of persistent pulmonary hypertension (PH), despite correct treatment of PE, lead to the diagnostic suspect. The first choice treatment is pulmonary endarterectomy (PEA) associated with lifelong anticoagulant therapy with vitamin K antagonist. We present the case of a 53-year-old male affected by dyspnea for months, admitted to a sub-intensive care unit for intermediate low-risk PE; echocardiography showed signs of PH persisting after anticoagulant therapy; after 2 months of specific treatment the diagnosis of CTEPH was confirmed and the patient was successfully treated with PEA.