While it is known that the process of becoming literate begins in early childhood and usually involves several years of schooling, research related to cognitive characteristics has been done mostly on illiterate adults, and information concerning illiterate children is therefore limited. The aim of the present study, involving 21 illiterate and 22 literate Mexican children aged 6 to 13, was to investigate the effects of literacy on neuropsychological characteristics during childhood. The children's performance on 16 cognitive domains of the "Evaluacion Neuropsicologica Infantil" (ENI, Child Neuropsychological Assessment) was examined in three mixed within- and between-groups profile analyses. The results suggest that the effect of literacy observed in adults is already evident in children in almost every task analysed. Moreover, the fact that an age effect was detected for the calculation abilities suggests that maths learning is school- and environment-dependent.