A cross-sectional study using 92 children aged 6 to 13 years investigated the dimensionality and the development of executive functioning. The measures were drawn from developmentally relevant conceptualizations of executive functioning and included a go/no-go task, a verbal fluency task, a continuous performance task, a Stroop-like task, a hand movements task, and a digit span task. Analyses revealed 3 dimensions interpreted as Disinhibition, Speed/arousal, and Working memory/Fluency. Age and sex differences were analyzed for the delineated functions, which means that the results may be taken to represent age effects at the level of specific processes within the executive domain rather than on single tests. Age-dependent changes in children's performance on all 3 dimensions were demonstrated, with 3 particularly active stages of maturation: early childhood (6-8 years of age), middle childhood (9-12 years of age), and during early adolescence. Sex differences were only found for the speed/arousal dimension. The results are discussed in terms of 2 developmental executive function frameworks (Barkley, 1997b; Roberts & Pennington, 1996), where inhibition and the interaction between inhibition and working memory, respectively, are seen as key in the development of executive functioning.