Background The present study aimed to examine the experience of actual electronic cigarette (e-cigarette) use in smoke-free areas of restaurants and workplaces and to explore the determinants associated with such use among Japanese adults who reported any experience using e-cigarettes (e-cigarette ever-users).

Methods An Internet-based self-reported questionnaire survey was conducted in 2015 on Japanese e-cigarette ever-users. The proportion of the respondents who had ever used or frequently used e-cigarettes in smoke-free restaurants and/or workplaces was calculated. Potential factors associated with e-cigarette use in those smoke-free areas were also examined by using multivariable logistic regression analyses.

Results In total, 1243 e-cigarette ever-users (662 current and 581 former e-cigarette users) were analysed. The majority of them (1020/1243, 82.1%) were male and their mean age ± SD was 47.0±10.4 years. The proportion of those who had ever used e-cigarettes in smoke-free restaurants was 28.8% (358/1243) and that in smoke-free workplaces was 25.5% (317/1243), respectively. The proportion of those who had frequently used e-cigarettes in smoke-free restaurants was 18.5% (230/1243) and that in smoke-free workplaces was 16.3% (202/1243), respectively. In general, the proportion of e-cigarette use in those smoke-free areas was higher among those having a higher educational level than those having a lower educational level.

Conclusion Among adult Japanese e-cigarette ever-users, approximately 26%–29% had ever used and 16%–19% had frequently used e-cigarettes in restaurants and/or workplaces where combustible tobacco smoking is not allowed. Policy-makers may need to establish explicit rules as to e-cigarette use in smoke-free environments.