BACKGROUND Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare form of pulmonary hypertension which is often caused by recurrent emboli. The reported prevalence in Latvia is 15.7 cases per million inhabitants. Several risk factors predispose patients to develop chronic thromboembolic pulmonary hypertension, including the presence of chronic myeloproliferative diseases and splenectomy. CASE REPORT We present a case of a 68-year-old woman with a variant of chronic myeloproliferative disease, essential thrombocythemia, splenectomy, and chronic thromboembolic pulmonary hypertension, in whom chronic thromboembolic pulmonary hypertension was mimicking acute pulmonary embolism. On admission, the patient had progressive dyspnea, elevated right ventricular systolic pressure (RVSP) 60-70 mmHg, and elevated thrombocytes, C-reactive protein, BNP, and d-dimer levels. These results, as well as the results of thoracic computed tomography angiography with contrast, supported the diagnosis of acute pulmonary embolism. During the sequent follow-up visit after 3 months of effective anticoagulant therapy, the patient had elevated RVSP: 55-60 mmHg. Therefore, right heart catheterization was performed, in which it was found that mPAP was 37 mmHg with PCWP 5 mm Hg and PVR 8.9 Wood units, confirming the CTEPH diagnosis. CONCLUSIONS Patients who are at high risk of thrombosis need an increased level of monitoring to be properly evaluated. An easy solution to misdiagnosis of CTEPH with an acute pulmonary embolism could be taking scrupulous patient history, which can reveal multiple risk factors of CTEPH development. The subsequent assessment of risk factors can lead to a more appropriate consideration of CTEPH diagnosis vs acute pulmonary embolism.