The aim of the present study was to investigate whether preschool children with limitations in the visual or phonological working memory are disadvantaged in the acquisition of school relevant precursor skills at school entry. A sample of 92 children was divided into three subgroups depending on their performance in visual and phonological working memory tasks in their last year before school entry (T[subscript 1]). At T[subscript 1] the children were tested on cognitive measures as well as quantity-number competencies and phonological awareness tasks. Shortly after school entry (T[subscript 2]), the precursor skills were assessed again. The findings indicate that preschool children with reduced phonological working memory capacity show weaker numerical competencies before school entry and weaker phonological awareness skills at the beginning of school compared to an unimpaired control group. On the other hand, visual working memory limitations in preschool only affect numerical competencies before and particularly after school entry. (Contains 4 tables.)