Little is known about the risk and addiction perceptions of e-cigarettes among Asian populations. We examined e-cigarette perceptions among young adults in Hong Kong and the association between the perceptions and e-cigarette use patterns.An online survey was administered to a convenience sample of Hong Kong residents aged 18-35 (N = 1186). Measures of e-cigarette perceptions included perceived harm and addictiveness of e-cigarettes, perceived harm of secondhand e-cigarette aerosol, and perceived popularity of e-cigarette use among peers. Separate multinomial logistic regression models were conducted to examine the associations between the four perceptions and former and current use of e-cigarettes relative to never use, controlling for demographics and current cigarette smoking status. Interactions of e-cigarette perceptions and current cigarette smoking were assessed in all models. Among current e-cigarette users, bivariate exact logistic regression models were used to examine the relationships between each of the perceptions and frequent e-cigarette use (≥3 days in past 30-day vs. 1-2 days). Among participants who had never used e-cigarettes, separate multivariable logistic regression models were conducted to examine the associations between e-cigarette perceptions and susceptibility to e-cigarette use.Overall, 97.2% of participants were aware of e-cigarettes, and 16.1% had tried e-cigarettes (11.3% former users; 4.8% current users). Young adults perceived e-cigarettes (and aerosol) as less harmful, less addictive, and less popular than cigarettes. Current cigarette smokers reported significantly lower perceived harmfulness and addictiveness of e-cigarettes, lower perceived harmfulness of e-cigarette aerosol, and higher perceived popularity than nonsmokers. The lower degree of harm and addiction perceptions, and higher levels of popularity perceptions were associated with greater odds of e-cigarette use, and these relationships were generally stronger among nonsmokers compared to current cigarette smokers. E-cigarette perceptions were not associated with frequent e-cigarette use. Perceiving e-cigarettes (and aerosol) as less harmful and less addictive were associated with greater susceptibility to e-cigarette use. Compared to nonsmokers, current smokers were more likely to report e-cigarette use and susceptibility.Continued monitoring of e-cigarette use and perceptions is needed. Educational programs should emphasize the potential harmful and addictive properties of e-cigarettes and the risks of secondhand exposure to e-cigarette aerosol.