BACKGROUND: The frequent coexistence of obesity and arterial hypertension is well known. Although both conditions have been identified as independent risk factors for impaired left ventricular diastolic function, there is a paucity of data on the dysfunction among obese patients with newly diagnosed arterial hypertension. The study was performed to determine the prevalence of diastolic dysfunction in obese individuals with newly diagnosed arterial hypertension and to compare it with the prevalence in normotensive obese persons. METHODS: We enrolled 125 obese patients: 65 with newly diagnosed hypertension and 60 normotensive patients matched for age, sex and body mass index. Left ventricular diastolic function was assessed from the following Doppler-echocardiographic measurements: mitral inflow velocities (E and A wave), E wave deceleration time, isovolumetric relaxation time, left atrial and left ventricular diameters, left ventricular wall thickness and left ventricular heart mass index. Diastolic dysfunction was considered when the E/A ratio was <1. RESULTS: We found significantly higher A wave, lower E/A ratio, longer E deceleration time and a bigger left atrium in obese patients with newly diagnosed arterial hypertension. We did not find significant differences in E wave peak velocities between the two groups. Although there was no difference in left ventricle heart mass or the prevalence of left ventricle hypertrophy, the prevalence of diastolic dysfunction was higher in the group with newly diagnosed arterial hypertension. CONCLUSION: This study suggests that newly diagnosed arterial hypertension significantly contributes to impairment of left ventricular diastolic function in obese patients before development of structural aberrations detectable on echocardiography.