We studied vitamin D intake, serum 25-hydroxyvitamin D (S-25(OH)D) concentration, determinants of S-25(OH)D and risk factors for S-25(OH)D <50 nmol/l in a population sample of Finnish children. We studied 184 girls and 190 boys aged 6���8 years, analysed S-25(OH)D by chemiluminescence immunoassay and assessed diet quality using 4-d food records and other lifestyle factors by questionnaires. We analysed the determinants of S-25(OH)D using linear regression and risk factors for S-25(OH)D <50 nmol/l using logistic regression. Mean dietary intake of vitamin D was 5��9 (sd 2��1) ��g/d. Altogether, 40��8 % of children used no vitamin D supplements. Of all children, 82��4 % did not meet the recommended total vitamin D intake of 10 ��g/d. Milk fortified with vitamin D was the main dietary source of vitamin D, providing 48��7 % of daily intake. S-25(OH)D was <50 nmol/l in 19��5 % of children. Consumption of milk products was the main determinant of S-25(OH)D in all children (standardised regression coefficient ��=0��262; P<0��001), girls (��=0��214; P=0��009) and boys (��=0��257; P=0��003) in multivariable models. Vitamin D intake from supplements (��=0��171; P=0��035) and age (��=���0��198; P=0��015) were associated with S-25(OH)D in girls. Children who drank ���450 g/d of milk, spent ���2��2 h/d in physical activity, had ���13��1 h/d of daylight time or were examined in autumn had reduced risk for S-25(OH)D <50 nmol/l. Insufficient vitamin D intake was common among Finnish children, one-fifth of whom had S-25(OH)D <50 nmol/l. More attention should be paid to the sufficient intake of vitamin D from food and supplements, especially among children who do not use fortified milk products.