Background: Psychometric instruments are used increasingly within research and clinical settings, and therefore standardization has become an important prerequisite, even for investigating very young children. Currently, there are no standardized psychometric instruments available for assessment of preschool children in Denmark. Aims: The aim was to achieve Danish national norm scores for the Child Behavior Checklist for Ages 1(1/2)-5 (CBCL/1(1/2)-5) and the Caregiver Report Form (C-TRF). Methods: The study was based on an age- and gender-stratified cohort sample of 1750 children aged 1(1/2)-5 years born at Aarhus University Hospital, Denmark. The CBCL/1(1/2)-5 and C-TRF were mailed to parents, who were asked to pass on the C-TRF to the preschool caregiver. The national standard register data gave access to information on socio-economic status, family type, ethnicity and parental educational level for analysis of participation and representation. Results: A total number of 850 (49%) families replied, and 624 caregivers replied. The mean Total Problem Score (TPS) with 95% confidence interval was 17.3 (16.3-18.3) for parents' reports. Age-and gender-specific scale score findings for Danish preschoolers and schoolchildren were comparable. No differences were found in the mean TPS within subgroups related to parental socio-demographic features. Conclusion: On the basis of a large sample, Danish national norm scores and profiles of the ASEBA Preschool Forms were established; the scores of descendents must, however, be assessed with some caution. With this reservation, the CBCL/1(1/2)-5 and C-TRF forms are now available in Danish and can be recommended for use in clinical and research settings.