We have investigated angiotensin II type 1 receptor (AT2R1) gene polymorphism (A1166C) and its influence upon efficiency of olmesartan treatment in patients with essential hypertension. A total of 58 hypertensive patients, mean age (54.4±9.6) years, were examined, 58.6 % were women and 41.4 % – men. Among them 32 (55 %) patients received olmesartan 20 mg daily: 18 (56.25 %) patients as monotherapy, 14 (43.75 %) patients – olmesartan in combination with other antihypertensive agents (AHA). Duration of follow-up was 6 months. Patients were examined with electrocardiography, echocardiography, ambulatory blood pressure monitoring (ABPM), registration of central aortic pressure (CAP) with applanation tonometry of radial artery using SphygmoCor device, determination of serum lipids and creatinine and the genetic analysis of AT2R1 gene polymorphism in buccal epithelial cells using the polymerase chain reaction. Genetic testing of AT2R1 gene polymorphism revealed following distribution of genotypes: AA genotype – 24 (41.4 %) patients, AC – 32 (55.2 %) and CC – 2 (3.4 %) patients. Irrespective of the genotype, olmesartan provided significant reduction of the office brachial systolic and diastolic blood pressure. At the same time, evaluation of ABPM indexes and parameters of CAP after treatment with olmesartan demonstrated significant decrease of main characteristics according to these methods only in patients – carriers of abnormal allele C. Thus, in patients with essential hypertension AT2R1 gene polymorphism (A1166C) has a significant impact upon efficiency of antihypertensive therapy as measured by ABPM and CAP.