Dietary patterns are useful in nutritional epidemiology, providing a comprehensive alternative to the traditional approach based on single nutrients. The Cardiovascular Risk in Young Finns Study is a prospective cohort study with a 21-year follow-up. At baseline, detailed quantitative information on subjects' food consumption was obtained using a 48 h dietary recall method (n 1768, aged 3-18 years). The interviews were repeated after 6 and 21 years (n 1200 and n 1037, respectively). We conducted a principal component analysis to identify major dietary patterns at each study point. A set of two similar patterns was recognised throughout the study. Pattern 1 was positively correlated with consumption of traditional Finnish foods, such as rye, potatoes, milk, butter, sausages and coffee, and negatively correlated with fruit, berries and dairy products other than milk. Pattern 1 type of diet was more common among male subjects, smokers and those living in rural areas. Pattern 2, predominant among female subjects, non-smokers and in urban areas, was characterised by more health-conscious food choices such as vegetables, legumes and nuts, tea, rye, cheese and other dairy products, and also by consumption of alcoholic beverages. Tracking of the pattern scores was observed, particularly among subjects who were adolescents at baseline. Of those originally belonging to the uppermost quintile of pattern 1 and 2 scores, 41 and 38 % respectively, persisted in the same quintile 21 years later. Our results suggest that food behaviour and concrete food choices are established already in childhood or adolescence and may significantly track into adulthood.