With the emergence of non-invasive methods like magnetic resonance imaging (MRI) and functional MRI (fMRI), there is growing evidence of maturational changes in both neuro-anatomical structures and neural activation patterns. Developmental changes have been shown to last until adolescence. In study 1, we examined the impact of steroids on the developing brain and found that amygdala and hippocampal as well as parietal volumes were associated with circulating testosterone levels. In the studies 2 to 5 we adressed differences in brain activation patterns of attention between children and adults, where children were either normally developing children or children with ADHD. We found differences in the developmental trajectories in the fronto-striatal pathway between children with and without ADHD, as well as an increase in brain connectivity in a fronto- parietal network with adolescence. We conclude, that the puberty might have organizational effects on the developing human brain, which manifests itself in both, brain structure and function.