OBJECTIVE: To investigate differences in different aspects of social participation and social capital among baseline daily smokers that had remained daily smokers, become intermittent smokers, or stopped smoking at one year follow up. Design/setting/participants/measurements: 12 507 individuals, aged 45-69 years, interviewed at baseline between 1992 and 1994 and at a one year follow up were investigated in this longitudinal study. The three groups of baseline daily smokers were compared to the reference population (baseline intermittent smokers and non-smokers) according to different aspects of social participation and social capital. A multivariate logistic regression model was used to assess differences in different aspects of social participation and social capital. RESULTS: The baseline daily smokers that remained daily smokers at the one year follow up had significantly increased odds ratios of non-participation in study circles in other places than at work, meeting of organisations other than unions, theatre/cinema, arts exhibition, church, sports events, large gatherings of relatives, and private parties compared to the reference population. The baseline daily smokers that had become intermittent smokers at the one year follow up had significantly increased odds ratios of non-participation in church services. The baseline daily smokers that had stopped smoking had increased odds ratios of non-participation in having attended a meeting of organisations other than labour unions during the past year, having been to a theatre or cinema, and of having visited an arts exhibition during the past year. All three categories of baseline daily smokers had significantly decreased odds ratios of non-participation in night club/entertainment. CONCLUSIONS: The baseline daily smokers that had remained daily smokers at the one year follow up had particularly high rates of non-participation compared to the reference population in both activities specifically related to social capital, such as other study circles, meetings of organisations other than labour unions, and church attendance and cultural activities such as theatre/cinema and arts exhibition, although significantly lower participation in cultural activities and meetings of other organisations was also observed among daily smokers that had stopped smoking. All three baseline daily smoker groups had higher rates of having visited a night club during the past year. [ABSTRACT FROM AUTHOR]