A study of blood lipid levels in adolescent students in rural and urban areas of Greece was undertaken. Blood samples were drawn from 307 adolescents aged 12 to 18 years attending two rural and two urban high schools of different socioeconomic level (urban/lower, urban/higher). Obesity among adolescents had statistically significant detrimental effects on the lipids profile, being associated with higher total and low-density-lipoprotein (LDL) cholesterol and lower high-density-lipoprotein (HDL) cholesterol levels. Adolescents living in urban areas had substantially and significantly higher levels of total and LDL cholesterol, but among urban residents, higher socioeconomic status was associated with lower levels of total and LDL cholesterol. There was no clear evidence that total, LDL, and HDL cholesterol levels were substantially affected by qualitative aspects of diet as evaluated through a food frequency questionnaire. The results of this study indicate that the traditional Mediterranean pattern of living and eating in the rural areas of Greece is associated with a favorable lipid profile in adolescents, which may explain the very low incidence of coronary heart disease (CHD) in these areas. In urban areas lipid profiles are satisfactory in children of high socioeconomic status but unfavorable in children of low- to middle-class families, which are known to be at higher risk for CHD.