Background and aims: Familial hypercholesterolemia (FH) is a genetic disorder characterized by elevated levels of low density lipoprotein (LDL) cholesterol and increased risk of premature cardiovascular disease (CVD). The treatment of FH involves lipid-lowering drug therapy and dietary counseling, the latter being the primary treatment in children. The observed lipid lowering- and CVD preventing effects of certain dietary patterns in the general population support the inclusion of dietary counseling in the treatment of FH. Still, the effects of lipid lowering dietary treatment in this disease are not clear. Possible different effects of maternal and paternal inheritance of FH are also a largely unexplored field. The aim of this thesis is to increase knowledge about the diet of children with FH, to compare their diet to that of other non-FH children, and to investigate the relation between a dietary score and blood lipids. In addition we wanted to explore whether paternal/maternal FH affect dietary score, blood lipids and C-reactive protein (CRP) differently. Subjects and methods: The diet of 112 children and young FH subjects (of which 43 were between 11 - 15 years) and 29 children without FH (aged 13 years old) was investigated by use of the SmartDiet questionnaire. The SmartDiet scores and the use of different food items of the FH children aged 11-15 years old were compared to those of the children without FH. (The SmartDiet scores and the use of different food items among the entire group of FH subjects were also analyzed.) Blood lipid levels of the FH subjects were retrieved from their medical records at the Lipid Clinic, and blood lipid levels were obtained from the non-FH children. The relations between SmartDiet scores and lipid levels were analyzed. Lipid levels of FH subjects with maternal and paternal FH were compared, as were their SmartDiet scores. Results: The FH children aged 11-15 years had significantly higher SmartDiet scores than the non-FH children. (The score of the subgroup of FH children was very similar to that of the entire FH group.) Both the FH subjects and the non-FH children could improve diet to make it healthier. Regarding the use of different foods, the FH children aged 11-15 differed from the non-FH children as significantly higher proportions of the FH children used low-fat products among types of milk, meat and cheese or products high in unsaturated fatty acids when choosing butter/margarine. No differences were observed regarding use of fruits/vegetables/berries, fish, grain products high and low in fiber or snacks. A significantly higher proportion of the FH children used sweet spreads/sweet drinks. No significant correlations were observed between lipid levels and SmartDiet scores, except a moderate inverse correlation with triglycerides level among the non-FH children. SmartDiet scores of FH subjects with maternal FH did not differ from the SmartDiet scores of those with paternal FH. No significant differences in lipid levels or CRP were observed between FH subjects with maternal/paternal FH among those who were not statin treated. Among those who were statin treated, FH subjects with paternal FH had significantly lower apo B/apo A1 ratio than those with maternal FH. Conclusion: Our results suggest that FH children have a healthier diet than non-FH children, and that the dietary treatment that they, and their parents, receive is effective in terms of promoting healthy food choices. However, there appears to be considerable room for improvement regarding healthiness and “heart-friendliness” of the diet of children and young FH subjects as well. We found no relationship between diet and blood lipids in FH children in this study. Larger, better controlled studies with more comprehensive dietary assessment methods should be conducted in order to investigate this further. Maternal/paternal FH does not seem to influence the healthiness of diet in children and young with FH differently. Whether inflammation and lipid levels differ between FH subjects with maternal/paternal FH needs to be further investigated.