This paper analyses cause-specific mortality in ages 15–30 years in Finland, using longitudinal population register data that covers the period 1970–2004. The aim is to see how mortality risks interrelate with living conditions in the parental home and with regional confounders, in order to understand why the two native population groups of the country differ in mortality. Results based on Cox proportional hazard models reveal that, in young men, socio-economic circumstances interrelate with external causes of death excluding suicides, probably because of social class differences in hazardous lifestyles. Thus injuries and accidents, but not suicides, depend on socio-economic background. For suicides, we find a regional mortality pattern that is highly similar to variation in overall mortality at higher ages, whereas for all other external causes of death such differences cannot be observed. These results suggest that hereditary factors cannot be ruled out as an explanation to the population-group mortality gradient.