We investigate the relationship between inhibition and cognition in developmental age adding values for the understanding of EFs. The aim of this study was to examine the development of EFs by comparing children of different clinical populations: children with a Mild Intellectual Disability (MID) with atypical cognitive development and children with ADHD inattentive subtype with impaired inhibition development. Results obtained suggest that only a subgroup of MID has an inhibition deficit (not overlapping with ADHD). So, the data seemed to support the hypothesis that EFs, even when impaired, could follow different pathways of development, partially independent from intelligence. Moreover, our findings seemed to fit with the hypothesis that the diagnosis of intellectual disability include different neuropsychological phenotypes.