BACKGROUND Cigarette smoking is one of the most common habits of the modern world. The World Health Organization (WHO) showed that about 30% of the world's population over the age of 15 smoked cigarettes. That gives the number of 1.1 billion smokers. It is known that the habit of smoking is a serious risk to human health and life. Cigarette smoke induces the formation of reactive oxygen species (ROS). ROS can cause direct damage of DNA chain and leads to the mutagenic and carcinogenic effect. OBJECTIVE To evaluate the concentration of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the urine of smokers. Based on the obtained results an attempt to determine whether the concentration of 8-OH-dG in the urine can be an indicator of genotoxicity of tobacco smoke. METHODS The study was conducted in 83 healthy volunteers, 63 smokers and 20 non-smokers (control group). The age of patients in both groups were in the range 20-60 years. Average age of women and men in the control group and the test group was 34 years. Duration of smoking was 1-30 years, the number of cigarettes smoked from 1 to over 20 per day. In the urine the concentration of 8-OH-dG was determined using Bioxytech® 8-OH-dG-EIA™Kit (manufactured by OXIS International, Inc., Portland, USA) and the concentration of creatinine using in vitro diagnostic kit BIOLABO. The concentration of 8-OHdG in urine was expressed in ng/g creatinine. RESULTS More than 3-fold increase in the concentration of 8-OHdG in the urine of smokers was found. The increase in the concentration of 8-OHdG in the urine depended on age, the amount of smoked cigarettes per 24 hours, duration of smoking and cigarette brands. CONCLUSIONS The increase in the concentration of 8-OHdG in the urine of smokers, both women and men indicates DNA damage and the genotoxicity action of cigarette smoke. According to our previously conducted studies and examinations of other authors, it can be suggested that the concentration of 8-OHdG in urine may be considered as the sensitive and specific marker of oxidative DNA damage.