Electronic cigarettes represent a distinct type of nicotine delivery system that relies on heat rather than combustion to convert a solvent into an aerosol. It consists of a power source, a heater, and a liquid. E-cigarette use has expanded markedly worldwide. The surge in its use is more in adolescents and young adults and is partially attributed to e-cigarette advertising, which has increased the odds of using e-cigarettes. Another contributing factor is the belief that e-cigarettes are a safe alternative to traditional cigarettes. Most vapers have started using e-cigarettes with the belief that it is less harmful than conventional cigarettes, and with the hope that vaping will help them stop or at least reduce smoking. Despite that belief, there is a marked variation in self-reported abstinence or reduction rates among smokers who started using e-cigarettes. This chapter reviews the prevalence of e-cigarette smoking, associated beliefs, and their impact on smoking cessation.