Structural and functional damage of endothelium seems to be one of the most important factors of arterial hypertension evolution. Via release of vasoactive substances, particularly vasoconstrictors and vasodilators. The aim of the study was to assess the role of such vasodilators as L-arginine and nitric oxide (NO) in the pathogenesis of arterial hypertension in patients with obesity. Assessment of 103 hypertensive patients revealed two different patterns of changes in L-arginine--NO interrelation in those with obesity and normal BMI. In hypertensive patients with obesity mean NO concentration was approximately in normal range while in those with normal BMI NO levels increased up to 1.5 fold. Obesity depletes compensatory NO-synthetic mechanisms peculiarto endothelium of patients with stage I-II arterial hypertension.Two patterns of co-morbidity development depending on different levels of L-arginine and nitric oxide according to BMI were revealed.