Introduction The correlation of the right ventricular (RV) systolic function and functional capacity (FC) assessed by cardiopulmonary exercise testing (CPET) in HFrEF patients were demonstrated in previous studies In this study, we aimed to determine the correlation of RV free wall strain (RVfwlS) , left ventricular (LV) strain parameters and other standart echocardiographic parameters with the FC assessed by the 6 minutes walk test 6MWT in HfrEF patients. Also, according to the calculated RVfwlS, the differences among HFrEF patients were examined. Method Dilated cardiomyopathy patients with an EF lower than 40 % included in our study. After echocardiographic examinations, and venous blood sampling for NT-pro-BNP, the 6MWT performed for each participant by a physician blinded to echocardiographic examination. Results 50 patients with a mean EF of 28,78 ± 6,0 % were included. The distance walked in 6MWT ( 6MWT-dis) was significantly correlated with the NT-pro-BNP levels, E/Em-mean, left atrial volume index, RvfwlS, Sc (circumferential strain) and the Sl (longitudinal strain) . The Sc and the RVfwlS were found to be the independent predictors of the 6MWT-dis in multivariate analysis. According to mean RvfwlS which was -18,50 ± 4,83, we grouped patients; Group 1 (n= 26) RvfwlS > -18.5% and Group 2 (n=24) RVfwlS < -18.5%. The Group 2 patients have higher NT-pro-BNP levels (p<0.01) , lower 6MWT-dis (p<0.01), higher E/Em-mean (p<0.01) and lower Sl (p<0.01). Conclusion The low RVfwlS in HFrEF patients could indicate cumulative exposure of RV to chronic increased LV filling pressures due to LV remodelling and dilatation.