Background:
The objectives of this study are:
1) to describe the patterns of electronic cigarette (e-cigarette) use; and
2) to describe the prevalence of e-cigarette users who use in selected indoor public and workplaces, and private venues in Barcelona (Spain).

Methods:
This is a cross-sectional study of adult (>=18) current e-cigarette users and residents of Barcelona, Spain (n=600), recruited in 2015. We conducted a face-to-face questionnaire. We calculated percentages and odds ratios (OR) with their 95% confidence intervals (CI).

Results:
Of the total population, the most prevalent motivation for using e-cigarettes was to reduce tobacco smoking (48%) and the most prevalent flavor used was tobacco (49%). People younger than 25 years old (OR=4.36, 95%CI 1.99-9.57) and women (OR=1.87, 95%CI 1.02-3.43) were more likely to state their main motivation for use as to use where cigarettes were prohibited. Menthol and fruit flavors were more prevalent among women while fruit flavor was more frequent among the youngest age group. The highest proportion of participants who used e-cigarettes in public places was found at restaurants or bars (69.4%) and nightclubs or pubs (55.4%). Being current conventional tobacco smokers (dual users) was significantly associated with lower use of e-cigarettes in workplaces (OR=0.61, 95%CI:0.41-0.91), restaurants (OR=0.66, 95%CI:0.45-0.97) and nightclubs (OR=0.56, 95%CI:0.37- 0.86). 96.8% of e-cigarette users declared using the e-cigarette at home.

Conclusions:
Younger users of e-cigarettes are more likely than older individuals to use flavors other than tobacco and respond that the primary motivation for using is to be able to use where cigarettes are prohibited. Moreover, e-cigarette use in private settings and in public settings where their use is not regulated by law is high. Therefore, the public health administration should enact more expansive e-cigarette regulations.