Tobacco is the most popular overused substance in the world. There are two types of tobacco products: smoke and smokeless ones. The aim of this article is to explain the impact of tobacco on mucosa and describe the most common diseases of oral cavity among the tobacco users. The nicotine, the main component of tobacco, stimulates the central nervous system, addicting firmly and fast. The nicotine influences on metabolism of proteins and nucleic acids and disorders functioning of defense-andrepair system. The tobacco smoke provides also physical damages because increases temperature inside the mouth and burns tissues. In the clinical examination tobacco users have: hyperpigmentosis, black hairy tongue, superficial glossitis, periodontitis, leucoedema, nicotinic stomatitis, leukoplakia or neoplasm. Patients often claim on halitosis, bad taste or xerostomia. Dentistry provides a huge role on prevention, early detection of lesions and finally motivation for quitting smoking habits.