Introduction: In the United States, electronic cigarettes (e-cigarettes) are currently unregulated, extensively marketed, and experiencing a rapid increase in use. The purpose of this study was to examine the opinions of U.S. adults about e-cigarette use in smoke-free public areas. Methods: Data were obtained from the online HealthStyle survey administered to a probability sample of a nationally representative online panel. The study included 4,043 U.S. adults, aged 18 years or older who responded to this question, "Do you think e-cigarette should be allowed to be used in public areas where tobacco smoking is prohibited?" Multinomial logistic regression analyses were used to examine opinions on e-cigarette use in smoke-free areas by sex, age, race/ ethnicity, household income, education, census region, and cigarette smoking status and e-cigarette awareness and ever use. Results: Overall, about 40% of adults were uncertain whether e-cigarettes should be allowed in smoke-free areas, 37% opposed, while 23% favored their use in smoke-free public places. Multinomial logistic regression analyses showed that adults who were aware, ever used e-cigarettes, and current cigarette smokers were more likely to express an "in favor" opinion than adults who expressed an uncertain opinion (don't know). Conclusion: Over 75% of U.S. adults reported uncertainty or disapproval of the use of e-cigarettes in smoke-free areas. Current cigarette smokers, adults aware or have ever used e-cigarettes were more supportive to exempting e-cigarettes from smoking restrictions. With impending regulation and the changing e-cigarette landscape, continued monitoring and research on public opinions about e-cigarette use in smoke-free places are needed.