Coronary angiography is still the ‘gold standard’ in assessing the severity of stenotic lesions of the coronary arteries in the catheter laboratory. However, it is often difficult to identify the hemodynamic significance of one or another coronary artery stenosis, which is especially difficult in the case of borderline lesions with a coronary artery stenosis of 40–70 % according to angiography. It is important to note that the results of performed PCI are still largely assessed only on the basis of control angiographic data. This is due to the fact that the largest difference between angiography and FFR is in the intermediate range, and in general there is much less variation between angiography and fractional blood flow reserve (FFR) in the severe and mild lesions. However, the results of studies evaluating FFR after PCI showed a wide range of FFR values after satisfactory results of stenting according to angiography data. This additionally confirms the thesis that only one angiography is limited in determining the ischemic boundaries after PCI, and the level of FFR values after PCI is directly related to the results in the long-term period. Percutaneous coronary interventions under the control of FFR allows the operator to improve the results of endovascular treatment of coronary lesions in patients with coronary heart disease. The use of FFR in a catheter laboratory contributes to an increase in the clinical and economic efficiency of procedures, which is achieved due to the fact that the determination of FFR before PCI can significantly reduce the number of stents implanted during PCI, as well as to avoid unnecessary PCI stages in the treatment of patients with lesions of the LMCA. In addition, FFR allows to timely optimize the results of suboptimal PCI, as well as to reduce the frequency of main adverse cardiovascular events in the long-term period.