This investigation is designed to examine the differential experiences of acute nicotine withdrawal between individuals who use electronic nicotine delivery systems (ENDs) and conventional cigarettes. Participants will be community-recruited conventional smokers or ENDs users interested abstaining from smoking for 24 hours. Findings will be used to understand how nicotine delivery systems impact the subjective experience of nicotine withdrawal. This, in turn, will inform the relative merits of utilizing ENDs as a harm reduction strategy for conventional cigarette use.