Theoretical framework
The theoretical framework of the intervention was based on the transtheoretical model of behaviour change and the protection motivation theory. Both models have been independently applied to study health behaviour change interventions.The transtheoretical model proposes a systematic relationship between the stages and processes of behaviour change. To apply the model, we therefore used several strategies to strengthen change (in this case, quitting smoking) or to achieve the next stage of change. To prepare smokers for quitting, we formulated messages based on an analysis of smokers’ quitting intention. Messages for smokers with weak quitting intention were based on consciousness raising, dramatic relief and environmental re-evaluation (see 