5 Instruments: The required baseline information related to demographics and background information will be confirmed at the preparation stage. ICSCs will collect these information from the smokers during the enrollment of the first visit. A structured questionnaire at 1- and 3- month from enrollment of ICSCs will be developed by adopting or modifying international and/or locally validated instruments. The questionnaire gathers information including smoking and quitting history, satisfaction and perceived-usefulness of the social networking services, risk perceptions of smoking, intention to quit smoking (stage of readiness to quit), antecedent factors of the Theory of Planned Behavior model (behavioural beliefs, outcome evaluations, normative beliefs, motivation to comply), pros and cons of smoking (decisional balance), self-efficacy to resist smoking, other lifestyle risk factors (drinking and physical activities), demographic information such as age, gender, marital status, education level and employment status.