Survey respondents and non-respondents differ in their demographic and socio-economic position. Many of the health behaviours are also known to be associated with socio-economic differences. We aimed to investigate how much of the excess mortality of survey non-respondents can be explained by the socio-economic differences between respondents and non-respondents. Questionnaire-based adult health behaviour surveys have been conducted in Finland annually since 1978. Data from the 1978 to 2002 surveys, including non-respondents, were linked with mortality data from the Finnish National Cause of Death statistics and with demographic and socio-economic register data (marital status, education and household income) obtained from Statistics Finland. The mortality follow-up lasted until 2006, in which period there were 12,762 deaths (7,994 in men and 4,768 in women) during the follow-up. Total and cause-specific mortality were higher among non-respondents in both men and women. Adjusting results for marital status, educational level and average household income decreased the excess total and cause-specific mortality of non-respondents in both men and women. Of the total excess mortality of non-respondents, 41% in men and 20% in women can be accounted for demographic and socio-economic factors. A part of the excess mortality among non-respondents can be accounted for their demographic and socio-economic characteristics. Based on these results we can assume that non-respondents tend to have more severe health problems, acute illnesses and unhealthy behaviours, such as smoking and excess alcohol use. These can be reasons for persons not taking part in population surveys.