Found in tobacco products, nicotine meets the criteria of a highly addictive drug. Nicotine is a potent psychoactive drug that induces euphoria, serves as a reinforcer of its use, and leads to nicotine withdrawal syndrome when it is absent.
Nicotine in cigarette smoke affects mood and performance and is the source of addiction to tobacco. While cigarette manufacturers have publicly denied that nicotine is an addictive drug, recent documents disclose that they have known and used the addictive properties of nicotine since the 1950s. Unfortunately, this misinformation led to the false belief that nicotine use is a habit and not an addiction. Source: Medscape: Reference
Source: NIDA: Tobacco Addiction