Research on somatisation or functional disorders, characterised by the subjective report of physical symptoms in the absence of clear physical pathology, in young children is limited. This study investigates the distribution, types and co-occurrence of parent-reported functional somatic symptoms (FSS) and their impairment in a population-based sample of Danish 5-7-year-old children. Data were obtained from a 5-7-year follow-up of the Copenhagen Child Cohort 2000. The entire study population included 3,000 randomly sampled children from the cohort. Among these FSS measures were obtained for 1,327 children. The newly introduced parent interview, the soma assessment interview, was used to assess the child's FSS. Impairing symptoms were defined as FSS that caused substantial discomfort, impairment of everyday life, absence from day-care or school and/or help-seeking in the health care system. The 1-year prevalence of any FSS was 23.2% (N = 308) and higher in girls than boys (27.6 vs. 18.8%, P < 0.0001). Impairing FSS were found in 4.4% (N = 58). Pain complaints, i.e. limb pain, headache and abdominal pain, were the most frequently reported FSS. Among the 308 children with FSS, 66 (21.4%) presented with two or more of these functional pain complaints, while 15 (4.9%) had all three types. The findings indicate that FSS are common health complaints in 5-7-year-old children. A subgroup with impairing FSS with a likely need of clinical intervention was identified. This suggests that a somatisation pattern may start early in life and call for future studies to include associated impairment in the investigation of childhood FSS.