Diabetes mellitus is one of the most prevalent metabolic disorders in the world, and in fact in many regions in the world it is actually the most common metabolic disorder. The role of Insulin resistance (IR) in cardiovascular diseases is unclear and deserves further investigation. The main objective of this study was to explore whether there is an association between IR and left ventricular diastolic dysfunction in patients with impaired glucose tolerance (IGT) and type 2 diabetes mellitus. We found significant differences among the patients in groups with normal glucose tolerance (NGT), IGT and diabetes regarding HOMA-IR and QUICKI (P<0.001 for both). The pulsed Doppler transmitral variables were significantly different between groups: E wave (P<0.001), A-wave (P=0.006) and E/A ratio (P<0.001). The E/A ratio correlated with HOMA-IR and QUICKI (P<0.001, for both). Multiple linear regression model showed that IR (assessed by QUICKI) was an independent correlate of diastolic dysfunction (P=0.034). In conclusion, in subjects with IGT and patients with type 2 diabetes, insulin resistance is associated with impaired diastolic function of the left ventricle.