Epidemiological data on the distribution, persistence, and clinical correlates of health anxiety (HA) in childhood are scarce. We investigated continuity of HA symptoms and associated health problems and medical costs in primary health services in a general population birth cohort. HA symptoms were assessed in 1886 Danish 11-12 year old children (48 % boys) from the Copenhagen Child Cohort using the Childhood Illness Attitude Scales (CIAS) together with information on socio-demographics and the child's somatic and mental status and healthcare expenditure. Non-parametric statistics and regression analysis were used to compare groups with low (n = 184), intermediate (n = 1539), and high (n = 161) HA symptom scores. The association between HA symptoms assessed at age 5-7 years and HA symptoms at ages 11-12 years was examined by Stuart-Maxwell test. HA symptoms were significantly associated with emotional disorders and unspecific somatic complaints, but not with chronic physical conditions. In regression analyses controlling for gender and physical comorbidity, healthcare expenditure peaked in children with the highest HA symptom score, that is these children used on average approximately 150 Euro more than children with the lowest score during the 2-year period preceding inclusion. HA symptoms at age 5-7 years were significantly associated with HA symptoms at age 11-12 years. We conclude that HA symptoms, including hypochondriacal fears and beliefs, were non-trivial in preadolescents; they showed continuity from early childhood and association with emotional disorders, unspecific somatic complaints, and increased healthcare expenditure. Further research in the clinical significance of childhood HA is required.