Aim: To investigate the left and right ventricular myocardial performance index in patients with coronary slow flow phenomenon and to determine the relationship between it and thrombolysis in myocardial infarction frame count in SCF patients. Material and methods: 45 patients with slow coronary flow; mean age 51 ± 12 years and 20 subjects with angiographically normal coronary; mean age 52 ± 12 years, were included in the study. All the subjects underwent echocardiography and tissue Doppler imaging to determine left & right ventricular diastolic functions and myocardial performance index (MPI). Results: The TDE parameters obtained from the left and right ventricles showed. LV Sm, and Am, was similar in both the SCF and control groups; however, LV Em, Em/Am, IRT and MPI were significantly different in the SCF group compared to the control. RV wall Sm, and Am were similar in both the SCF and control groups however, RV Em, Em/Am, IRT and MPI were significantly different in the SCF group compared to the control. Patients had significantly higher TFC for each major epicardial coronary artery (P < 0.001). TFC was positively correlated with the left ventricle MPI index (r = 0.61, p < 0.001), the right ventricle MPI index (r = 0.49, p < 0.001), and mitral IVRT (r = 0.61, p < 0.001). There was a strong inverse correlation between mean TFC and left ventricle Ea and Ea/Aa ratio (r = -0.70, p < 0.001; r = -0.45, p = 0.001, respectively). Conclusion: Left and right ventricular diastolic functions deteriorated in the CSF phenomenon and this deterioration was associated with increased TIMI frame count.