Participants will be surveyed by trained interviewers through face-to-face interviews using a structured standardized questionnaire, including information on: i) socio-economic and demographic characteristics; ii) cigarette smoking habit and e-cigarette use; iii) SHS and e-cigarette aerosol exposures in different sites; iv) attitudes and perceptions on smoke-free regulations. Whenever possible, data will be collected within computer assisted personal interviews (CAPI). Alternatively, paper and pencil (P&P) interviews will be accepted.