Participants
We enrolled 5293 daily smokers in the randomized trial. The one-month follow-up questionnaire was completed by 1861 participants (35% of 5293), and the six-month follow-up questionnaire was completed by 1407 participants (27% of 5293). Only the 1407 participants who answered the six months questionnaire were included in the analyses of smoking cessation. Only the 673 participants who were still smoking after six months and provided information on cig./day both at baseline and at 6 months were included in the analyses of change over time in cig./day. Only the 502 participants who had quit smoking after one month (criterion: no smoking in the last 7 days) and who responded after 6 months were included in the analyses on relapse.