The Lipoprint system (Quantimetrix Corp., CA, USA), enables the determination of 10 high density lipoprotein (HDL) subfractions in contrast to the 5 HDL subfractions that can be determined by ultracentrifuge analysis. HDL subfractions, and their relationships to the arylesterase (PON1-A) and lactonase (PON1-L) activities of paraoxonase 1 (PON1), together with total-, very low density lipoprotein- and low density lipoprotein (LDL)-cholesterol and LDL subfractions were investigated in the serum of 27 mildly hypercholesterolemic children and 21 healthy controls. Our results suggest the antiatherogenity of large HDL (L-HDL) subfractions and the atherogenity of small HDL (S-HDL) subfractions in the study groups. However, the relationship between the intermediate HDL (I-HDL) subfractions with the LDL subfractions and other lipoproteins did not suggest that I-HDL subfractions are antiatherogenic. No significant association between PON1-A and the HDL subfractions was found. In contrast, PON1-L activity positively correlated with the antiatherogenic large HDL1 subfraction and negatively with intermediate HDL subfractions 4, 5 and 6. Our results contribute to the knowledge of the roles of total HDL and ten individual HDL subfractions in children and adolescents.