Serum Se concentrations and dietary Se intakes have been determined in relation to age, sex, ethnicity, region and index of deprivation in a nationally representative sample of New Zealand children aged 5–14 years from the 2002 National Children's Nutrition Survey. Dietary intake was assessed from computer-assisted, multiple-pass 24 h diet recall interviews (n 3275). Serum Se concentrations were obtained from a subset of urban-based children (n 1547). Mean (95 % CI) serum Se concentration in children was 0·96 (0·93, 1·00) μmol/l. Males (1·00 μmol/l) had higher serum Se levels than females (0·93 μmol/l; P = 0·027). Mäori children had lower serum Se than Pacific Islands children (P = 0·038) and New Zealand European and Other children (P = 0·005). Children in the Upper North Island (1·06 μmol/l) had higher mean serum Se values than those in the Lower North Island (0·98 μmol/l, P < 0·0005) and South Island (0·79 μmol/l, P < 0·0005), and serum Se in the Lower North Island was higher than that in the South Island (P < 0·0005). Mean dietary Se intake was 36 (34, 37) μg/d. The intakes of children aged 5–6 years (31 μg/d) were lower than those of children aged 7–10 and 11–14 years (35 and 38 μg/d, respectively; P < 0·00 005) and the intakes of 7–10-year-olds were lower than those of 11–14-year-olds (P = 0·002). Serum Se was associated with dietary Se after adjusting for all variables, including region (P = 0·006). The Se status of our children falls in the middle of the international range of serum Se concentrations, but that for children in the South Island is among the lowest values reported and may be a cause for concern.