There are marked differentials in mortality risks across regions in Finland. No exhaustive explanation to this variation has been provided, however. The aim of this paper is to analyse how geographic ancestry, as proxied by persons' birth region and population group, interrelates with cause-specific mortality risks. Focusing on people aged between their mid-thirties and late-forties, we use longitudinal population register data that offer opportunities to account for variables that represent both persons' social background and their own social status at young adult age. Results of Cox proportional hazard models say that these variables have substantial effects on mortality of different causes, but only a marginal impact on the variation in death rates by birth region and population group. The geographic mortality pattern is found to be specifically prominent for causes of death that are fairly unrelated to persons' lifestyles. Our findings suggest that genetic predisposal as expressed in terms of geographic ancestry might play a relevant role in understanding mortality variation within the population of Finland.