As part of the validation procedure of a new parent questionnaire ("Five to Fifteen" or the FTF) a random sample of 1500 children aged 5-13 years from the Swedish Population Register (SPAR) was approached. The FTF and the Child Behavior Checklist (CBCL) were sent to the parents of the children together with questions about background conditions. After two reminders the response rate was 55.6%. The final sample had a mean age of 9.12 years (SD=1.89) and a sex distribution with 55% boys and 45% girls. Analysis of attrition did not support overrepresentation of foreigners/immigrants in the attrition population. FTF like CBCL showed sensitivity to sociodemographic variables. On the FTF fewer problems were indicated for girls in all domain scales, whereas this was true for the summary scale Externalizing and Mixed problems of the CBCL. The effects of age and area of residence were slight, but parental education was negatively related to all domain scales of the FTF and to all the CBCL scales. The intercorrelations of the FTF and CBCL scales with common content showed substantial overlap supporting the validity of the FTF scales. The correlation between scales within the FTF however also indicates a substantial comorbidity. This is also supported by the substantial correlation between problem score of the FTF domains perception, language, motor skills and the CBCL scale scores Attention, Social problems as well as the summary scale Mixed problems. These findings indicate that problems with inattention and social relations are shared across the various problem domains. Factor analysis of the FTF subdomain scores resulted in two factors, one representing learning problems and the other behavioural/emotional problems. Despite the low response rate the representativity of the sample was supported by the fact that the total problem score of CBCL was very similar to that of another Swedish sample with a relatively high response rate. The finding of a frequency of AD/HD symptoms in the FTF rating corresponding to the figures of prevalence of AD/HD in several international epidemiological studies could also be seen as support for the relevance of the findings. Thus, the results give support to the usefulness of the FTF questionnaire as an instrument that can help in delineating specific problem areas within the field of child neuropsychiatry. Through the comparison with the CBCL the validity of the FTF for the parts that the two instruments share could be ascertained and the value of tapping a broader problem area could be elucidated.