Tobacco smoke is a mixture of substances which cause more than one biological response of the organism. All forms of tobacco consumption and in particular smoking is a widespread habit and is one of the most serious health risks. In the Czech Republic there are 29.2 % smokers among subjects aged 18-64 years. Smoking participates in total of at least 24 diseases. It causes 75 % chronic lung diseases which in the CR are the cause of ca 1 % deaths, they participate in the development of 30 % neoplastic diseases which in the CR are the cause of 22 % deaths and of 20 % cardiovascular diseases which in the CR are the cause of death in 56 %. Passive smoking is an important public health problem. In non-smokers, in particular in children, it is associated with a higher risk of the infections of the lower airways and the pulmonary parenchyma. Passive smoking has a negative impact also on immune mechanisms. Smoking is a serious health risk but also the most important cause of death, invalidity and morbidity which can be influenced by prevention.

        Key words: smoking, passive smoking, tobacco, tobacco smoke, nicotine, tar, malignity, cardiovascular diseases