Tobacco is an important agricultural product that is consumed all over the world. More than 8000 chemicals are reported to be present in tobacco, and a large number of these chemicals are known carcinogens, and hence is known to be one of the most significant contributors to the development of cancer of different body parts. These chemicals have been reported to alter both the genetic and epigenetic constituents of cells. Such changes involve point mutation, deletion, insertion, recombination, transversion, transition, and chromosomal aberrations including aneuploidy and polyploidy. The chemical composition of different types of tobacco has been reported to be different. In this article, brief information about tobacco plants; history, types and popularity of tobacco; its chemical composition; relation to cancer and other diseases and its effects on the molecular, epigenetic and genetic compositions have been highlighted.