Background Alcohol consumption among adolescents has declined considerably during the last two decades. However, it is unknown if these adolescents' alcohol consumption will remain low as they grow older. To our knowledge, this is one of the first studies that uses longitudinal data to examine if non-drinking adolescents have a lower alcohol consumption in young adulthood or if they catch up. Methods A self-report survey was distributed to a birth cohort (n = 794) born in 1997 in a Swedish region when cohort members attended ninth grade (age 14-15 years) in 2012. Responders were divided into non-drinkers and alcohol users and assessed again in their late teens (17-18 years) and young adulthood (20-21 years). Results In their late teens (17-18 years), non-drinkers at baseline consumed less alcohol and had a lower probability of harmful use compared with their alcohol-using peers. In young adulthood (20-21 years), these effects disappeared when adjustment was made for covariates. However, a stratified analysis showed that non-drinking adolescents low in conduct problems consumed less alcohol and had a lower probability of harmful use in young adulthood than alcohol-using peers. Conclusions This study suggests that the decline in alcohol use among adolescents in the past decades may be associated with a lower alcohol consumption in the late teens and young adulthood among those low in conduct problems. This may have promising implications for alcohol-related morbidity and mortality.