BACKGROUND In patients with recent myocardial infarction (MI) limited exercise capacity during physical activity is an important symptom and the base for future treatment. The myocardial injury after MI leads to both systolic and diastolic left ventricular (LV) dysfunction. OBJECTIVE The aim of this study was to assess the relevance of systolic and diastolic LV function for cardiopulmonary exercise capacity in patients with prior MI. METHODS Sixty-five consecutive patients after first MI without signs and symptoms of heart failure, aged 52 ± 6 years, were included in the study. The following echo parameters were evaluated: LV ejection fraction (LVEF), peak early and late diastolic velocities (E, A), deceleration time of E wave (dec t E), ratio of early trans-mitral to early annular diastolic velocities (E/e'), velocity propagation of early filling (Vp), and diameters and volumes of LV and left atrium (LA). CPET variables included: oxygen uptake at peak exercise (peak VO2), oxygen pulse (VO2 HR), VE/VCO2 slope, circulatory power (CP) and recovery half time (T1/2). RESULTS Significant correlations were demonstrated between peak VO2 and E/e' (p < 0.001), peak VO2 and dec t E (p < 0.001), VO2 HR and E/e' (p = 0.002) and between VE/VCO2 and E/e' (p < 0.001). Twenty patients with elevated LV filling pressure achieved significantly lower peak VO2 (1624 vs. 1932 ml, p = 0.027) VO2 HR (11.70 vs. 14.05, p = 0.011) and CP (287,073 vs. 361,719, p = 0.014). By using multivariate regression model we found that only E/e' (p = 0.001) and dec t E (p = 0.008) significantly contributed to peak VO2. CONCLUSIONS Diastolic dysfunction, particularly LV filling pressure, determine exercise capacity, despite differences in LV ejection fraction in patients with prior MI.