The present study explored the relationship between cognitive development and anxiety phenomena in 4-12-year-old children. Fears and worries of normal children (n=176) were compared to those of children with below-average intellectual abilities (children with BAIA; n=105). We evaluated to what extent level of cognitive development as indexed by a Piagetian conservation task was associated with the presence of fears and worries. While normal children and children with BAIA did not differ with regard to the content of their fears and worries, normal children more frequently reported such anxiety phenomena during the semi-structured Anxiety Interview than did children with BAIA. Furthermore, in normal children, evidence was found to suggest that level of cognitive development contributes to the experience of fears and worries. That is, anxiety phenomena were more prevalent among those children who passed a Piagetian conservation task. However, when anxiety phenomena were assessed by means of the Koala Fear Questionnaire (KFQ), a different picture emerged. KFQ data suggested that fears were less frequent in normal children and those children with BAIA who had a higher level of cognitive functioning. Apparently, the Anxiety Interview and the KFQ tap quite different aspects of anxiety. The KFQ seems to measure primitive fears that are likely to be prevalent among children with limited cognitive capacity, whereas the Anxiety Interview assesses more sophisticated anxiety phenomena that probably depend on high levels of cognitive functioning.