The aim of this study was to examine the intima-media thickness (IMT) of carotid arteries and endothelial function parameters such as plasma asymmetric dimethylarginine (ADMA) and homocysteine levels in hypercholesterolemic children and to investigate the relations of these parameters with hypercholesterolemia. Fifty-seven hypercholesterolemic and 37 healthy children were included in the study. Hypercholesterolemia was defined as 155 mg/dl and above for low-density lipoprotein (LDL)-cholesterol. Plasma concentrations of ADMA and homocysteine were measured and the measurement of carotid IMT was determined. Both carotid IMT and plasma ADMA levels were significantly higher in hypercholesterolemic children than healthy children (p<0.01). No significant difference was determined in homocysteine concentration between hypercholesterolemic children and the control group (p>0.05). No significant correlation was observed between lipid profiles and the levels of ADMA and homocysteine. However, a significant positive correlation was found between carotid IMT and total and LDL-cholesterol levels and between the levels of ADMA and LDL-cholesterol. In conclusion, the progressive increase in ADMA levels and carotid IMT and the positive relationship between carotid IMT and serum cholesterol levels support that plasma ADMA levels and carotid IMT can be indicators of early atherosclerosis in hypercholesterolemic children.