Background: Assessment of viable myocardium (VM) is one of the most important indications in examination of patients with ischemic heart disease and systolic dysfunction of the left ventricle (LV) before planned surgical revascularization. There is a clear dependence of survival of patients with ischemic cardiomyopathy (ICMP) on the quantity of VM. One of the main methods for the assessment of VM is SPECT/SPECT-CT myocardial perfusion imaging. The study aimed to evaluate the role of diagnostic capabilities of SPECT/SPECT-CT myocardial perfusion imaging in the assessment of VM in patients with ICMP and LV ejection fraction (LVEF) <35%. Material and methods: 48 patients with ICMP and LVEF <35% were examined. The age of the patients varied between 39 – 72 years, with an average of 52.5 ± 7.2 years. SPECT/SPECT CT myocardial perfusion imaging was performed on GE’s gamma camera “Infinia Hawkeye” at rest with ECG synchronization. A radiopharmaceutical (RFP) of 99mTc-MIBI with an activity of 7.5 MBq / kg was used. The results of the SPECT/SPECT-CT myocardial perfusion imaging were assessed using a quantitative approach, polar maps, and a 17-segment myocardium model. VM was considered at levels of accumulation of RFP more than 50%. The software ECToolBox and Myovation were used for assessment. Results: In right coronary artery – stenosis between 90-100%, the RFP absorption was 45.4 ± 12.7% (p <0.001), while the VM was 66.2 ± 6.9%. In 90-100% stenosis in the basin of the right interventricular branch of the left coronary artery, the RFP absorption was 57.2 ± 13.6% (p <0.05), VM – 54.8 ± 7.5%. In 90-100% stenosis in the basin of the envelope of the branch of the left coronary artery, the RFP absorption was 65.1 ± 9.7% (p <0.05), VM – 58.9 ± 5.6%. In patients with lesions of two or three coronary arteries, the RFP absorption was 42.6 ± 9.4% (p <0.001), while the VM was 35.3 ± 8.2%. Conclusions: SPECT/SPECT-CT myocardial perfusion imaging is a highly informative, noninvasive technique for the assessment of the quantity of viable myocardium in patients with ICMP and low LVEF.