Serum cholesteryl ester (CE) fatty acids, serum lipids and apolipoproteins were analysed from 1348 Finnish children aged from 3 to 18 years. The study was part of a comprehensive survey of coronary heart disease risk factors and their determinants in Finnish children and adolescents. The percentage of CE linoleate (18:2) had significant negative correlations with the serum concentrations of total and LDL cholesterol, triglycerides as well as apo B. The associations of HDL to CE fatty acids were weak, although there was a significant positive correlation of CE-18:2 to HDL cholesterol and apo A-I. The ratio of HDL to total cholesterol and the ratio of apo A-I to apo B increased strongly in quintiles of increasing percentage of CE-18:2. In conclusion, the present results show significant associations between serum CE fatty acid composition and the different components of serum lipoproteins among free-living Finnish children and imply a relation between the quality of dietary fats and serum lipoproteins within this population.