Objectives: To determine the contribution of different causes of death to absolute socioeconomic inequalities in mortality for the whole population of children of South Korea aged 1-4 years and 5-9 years. Methods: A cohort study based on the national birth and death registers of Korea was performed for 3 724 347 children born in 1995-2000 and 657 209 children born in 1995 to analyse mortality among children aged 1-4 and 5-9 years old, respectively. Adjusted mortality, risk difference (RD), slope index of inequality (SII), RR and relative index of inequality were calculated. The contributions of different causes of death to absolute mortality inequalities were calculated as percentages based on RD and SII. Results: Injuries other than from transport accidents contributed the most to total SIIs for male deaths at ages 1-4 (30.0% for father's education). The second largest contribution was from transport accident injuries (19.6% for father's education). For male deaths at ages 5-9, transport accident injuries and other injuries also accounted for most of the educational and occupational differentials in absolute mortality (63.5-90.5%). Patterns in cause-specific contribution to total inequalities in mortality among girls were generally similar to those among boys. Conclusions: The major contributing causes to absolute socioeconomic inequality in all-cause mortality for children aged 1-9 were external. To reduce the absolute magnitude of socioeconomic inequalities in childhood mortality, policy efforts should be directed towards injury prevention and treatment in South Korea.