Understanding how two characteristics--flavors and modified risk messages--affect perceptions and subjective effects of electronic cigarettes (e-cigarettes) can inform tobacco control efforts. In two within-subjects studies (N = 17 and N = 19), the effects of e-cigarette flavors (tobacco vs. menthol and unflavored vs. cherry) and hypothetical modified risk messages ("reduced harm relative to cigarettes" vs. no message and "reduced carcinogen exposure relative to cigarettes" vs. no message) on cigarette smokers' perceptions of e-cigarettes were measured after participants self-administered condition-specific products (own-brand cigarettes; e-cigarettes). Perceptions/subjective effects were tested using linear mixed-effects regressions. Cigarettes were perceived as most harmful but rated more positively than e-cigarettes (ps < 0.05). Cherry and menthol e-cigarettes increased perceived pleasantness, taste, and physical sensations compared with unflavored and tobacco-flavored e-cigarettes, respectively (ps < 0.05). Modified risk messages were associated with reduced ratings of aversive effects (ps < 0.05) but not harm perceptions. Overall, few perceptions/subjective effects differed by e-cigarette flavor or message. Flavors and messages may have some influence on how smokers experience e-cigarettes.