Assist. Prof. Nurten ELKİN in her speech; Cancer is an important public health problem that ranks second after cardiovascular diseases among deaths with known causes in the world and our country. At the same time, it causes very heavy losses in the economy and workforce of countries due to high treatment costs. However, considering that there are cancer types where treatment is possible and quality of life can be increased when diagnosed early, the importance of prevention increases even more. “1-7 April Cancer Week” activities, which are organized to intensify public information/awareness/raising awareness activities, have a very important place in the fight against cancer. However, keeping in mind that information, awareness-raising, and awareness-raising activities are not limited to one week of the year, but continued throughout the year will provide important gains in the fight against cancer. Among the environmental factors, cancers develop due to 90% environmental and 10% genetic factors; Today, it is known that it can be prevented by 30-50% by preventing tobacco use, alcohol consumption, being overweight and/or obese, and exposure to infections. The importance of prevention becomes even more important, especially when considering the types of cancer that can be prevented from occurring, death can be prevented by screening, and treatment can add a lot to the quality of life when diagnosed early. Smoking is the most important preventable cause of cancer worldwide. Many studies conducted to date have demonstrated the harmful effects of tobacco use on human health, based on strong epidemiological data. Tobacco use is the leading cause of preventable death worldwide. Numerous scientific studies conducted to date show that half of the tobacco users die due to a tobacco-related disease. Most tobacco-related death rates are due to Atherosclerotic Heart Disease (ASCH), Cancer, and Chronic Obstructive Pulmonary Disease (COPD). Tobacco use increases the risk of many other acute and chronic diseases, including cancer, in many organs other than the lung. In addition, diseases caused by the use of tobacco products during the current (COVID-19) period have directly constituted a risk factor for severe COVID-19 disease. There are thousands of chemicals in tobacco. Some of the tens of substances in tobacco, also known as carcinogens, trigger cancer directly, and some are suspected to trigger cancer. Among these carcinogenic substances, especially PAHs and N-nitrosamines, aromatic amines, ethylene oxide, 1,3-butadiene, and oxi radical damage are important substances. These carcinogens act by ingestion or absorption by the mucous membranes and lungs. In laboratory studies, it has been shown that the carcinogen DNA binary formation in tobacco smoke causes cancer. However, the development of cancer shows a lot of individual differences. Smokers are especially at high risk of developing lung, larynx, esophageal, and head and neck cancers. In addition, the relationship between smoking and leukemia, pancreatic, kidney, bladder, and cervix cancer has been proven. Cessation of tobacco use reduces the risk of developing a second use-related malignancy and improves the outcomes of cancer treatment. In the studies conducted, quitting tobacco use even during the diagnosis and treatment process of cancer patients prolongs cancer-related life expectancy.