Background: Emotions are important in smoking-related communications, but the role of discrete positive and negative emotions in comparative risk messages about combusted and electronic cigarettes (e-cigarettes) is unclear. Method: In an online experiment, 1,202 U.S. adult current smokers or recent quitters were randomized to view one of six messages about comparative risk of e-cigarettes and cigarettes. Participants reported their feelings of hope, happiness, fear, guilt, disgust, and anger and risk perceptions and behavioral intentions about e-cigarettes and cigarettes. Results: Hope was associated with higher perceived absolute cigarette risk, lower perceived absolute and comparative e-cigarette risk, and stronger intentions to quit smoking, seek quit help, use nicotine replacement therapy (NRT), switch to e-cigarettes, and use e-cigarettes exclusively versus dual use. Happiness was related to stronger intentions to seek quit help, use NRT, and switch to e-cigarettes but higher perceived comparative risk of e-cigarettes. Fear was associated with stronger intentions to quit smoking, seek quit help, use NRT, and switch to e-cigarettes. Guilt was related to higher perceived absolute cigarette risk, lower perceived comparative e-cigarette risk, and stronger intentions to use NRT. Disgust was associated with higher absolute and comparative e-cigarette risk and stronger intentions to quit smoking, seek quit help, and use e-cigarettes exclusively versus dual use. Anger was related to lower perceived absolute cigarette risk, higher perceived comparative e-cigarette risk, and weaker intentions to quit smoking. Conclusion: Comparative risk messages about e-cigarettes that arouse hope, fear, and guilt and avoid anger might be particularly likely to have positive impact on smokers.