The increase in levels of blood nicotine that occurs from smoking a single cigarette, sometimes referred to as a "nicotine boost," is an individualized measure of how much nicotine has been extracted from smoking a cigarette. This study investigated the demographic, smoking status, and psychological predictors of nicotine boost in a sample of 190 treatment-seeking smokers. Boost was assessed by comparing plasma nicotine levels before and after participants smoked one of their own brand cigarettes ad libitum. Positive affect (mood) was a significant positive predictor of nicotine boost, controlling for baseline cotinine levels and cigarette brand (Federal Trade Commission) nicotine delivery. However the proportion of variability accounted for in the model was relatively small (5%). Future research on individual differences in nicotine boost is warranted to clarify the role of psychological, physiological, and cigarette-related determinants.