Pulmonary embolism is recognized by WHO as one of the most common cardiovascular diseases and is diagnosed in about 0.15–0.20% of the population. It is the third most common cause of sudden death after coronary heart disease and stroke. Traditionally, this disease is spoken in the circle of vascular surgeons, cardiac surgeons, resuscitators. These are usually severe patients with massive thromboembolism and high risk for life. In this case, the diagnostic and subsequent tactics are obvious. At the same time, a huge contingent of patients with sub-massive pulmonary embolism and thromboembolism of small branches of the pulmonary artery are difficult to diagnose due to the variety of clinical manifestations. The purpose of the work was to conduct a clinical analysis of cases of the thromboembolism of small branches of the pulmonary artery. Material and methods. Twenty-four case histories of patients with the thromboembolism of small branches of the pulmonary artery who were treated at the departments of Pulmonology № 1 and № 2 of the Ivano-Frankivsk Center of Pulmonary Diseases in 2017 and 2018, were analyzed clinically and statistically. Among the examined patients were 17 (70.8%) men and 7 (29.2%) women. Patients' age ranged from 18 to 80 years and averaged 49.12 ± 2.75 years. The average length of hospital stay was 22.27 ± 1.77 days. Results. On admission, all patients complained of coughing. Most of them (79.1%) reported shortness of breath in combination with chest pain (75%), hemoptysis (45.8%) and hyperthermia (41.6%). One third of the patients had episodes of dizziness. From the anamnesis of patients' lives it is known that 5 (20.8%) of them were treated for recurrent pneumonia in the last year, 3 (12.5%) — for recurrent pleurisy, and 2 (8.3%) had recurrent hemoptysis. In 17 (70.8%) patients the diagnosis was verified by spiral computered tomography with contrast. Classical radiographic signs of the thromboembolism of small branches of the pulmonary artery and myocardial pneumonia occurred in only 3 (12.5%) patients. In most (58.3%) cases, changes in the chest X-ray were regarded as pneumonia. Two (8.3%) patients showed only signs of chronic bronchitis and emphysema. Ultrasound was informative, revealing signs of exudative pleurisy were in 11 (45.8%) patients. ECG and/or echocardioscope-signs of pulmonary heart were detected in 14 (58.3%) patients. D-dimer levels were determined in 18 (75%) patients. In all patients, this indicator was significantly higher than normal and averaged 5334.81 ± 9.75 ng FEU/ml. Based on a comprehensive examination of the causes of the thromboembolism of small branches of the pulmonary artery in this cohort of patients, the following were recognized: cardiac arrhythmias — in 6 (25%) patients, deep vein pathology — in 5 (20.8%) patients, hereditary thrombophilia — in 3 (12.5%)) patients, surgery — 2 (8.3%), tumors — 2 (8.3%). Unfortunately, in 25% of patients the causes of weight loss are not established. Conclusions. Despite the introduction of state-of-the-art high-information technologies into diagnosis, the thromboembolism of small branches of the pulmonary artery recognition remains a challenge for physicians. Diagnostic difficulties are due to the fact that the clinical picture of the thromboembolism of small branches of the pulmonary artery is characterized by non-specificity of symptoms and runs under the mask of various cardiac and respiratory diseases. Particularly important are alertness to the weight of physicians of different specialties, knowledge of the features of its multifaceted clinical picture and mahagement of such patients.