Adolescents with antisocial behaviour (ASB) have consistently shown structural abnormalities and dysfunctions of brain regions implicated in emotion and reward processing but little is known about the possible abnormalities in the functional and structural connections between different brain regions in this population compared to healthy non-antisocial adolescents. In this thesis we aimed to help reduce this knowledge gap. In part 1 we investigated resting state functional connectivity (RSFC) related to antisocial traits in two different groups of adolescents with antisocial behaviour (ASB).  In chapter 2, we found an association between different psychopathic traits and RSFC within and between resting state networks (RSNs) in a cohort of childhood arrestees. We showed that callous-unemotional traits were related to higher within-network connectivity of the frontopolar cortex in the default mode network (DMN), whereas impulsive-irresponsible traits were related to higher connectivity between the left fronto-parietal network (lFPN) and the inferior frontal network (IFN). We also showed increased between-network connectivity of the lateralized frontoparietal networks related to impulsive-irresponsible traitsThese findings suggest that different psychopathic traits in childhood arrestees are associated with different levels of connectivity within and between specific RSNs.  In chapter 3, we investigated the effect of a single dose of methylphenidate (MPH) on seed based RSFC of the nucleus accumbens (NAcc), amygdala and ventral tegmental area (VTA) centred networks in male adolescents with a Disruptive Behaviour Disorder (DBD). We found increased connectivity of the amygdala and NAcc with the DMN and visual networks in boys with DBD compared to healthy controls, and MPH normalized these aberrant connectivity patterns. This study suggests that MPH may normalize the increased functional connectivity of mesolimbic regions with areas involved in moral decision making, visual processing and attention in boys with DBD. In part 2 we studied how microstructural and macrostructural properties of white matter, reflecting structural connectivity, are related to antisocial traits in adolescents. In chapter 4, we investigated the specific relations of different psychopathic traits with the white matter microstructure in a cohort of childhood arrestees using diffusion tensor imaging (DTI). We found significant positive associations between grandiose-manipulative traits and fractional anisotropy (FA) in a large range of major white matter tracts. Callous-unemotional traits were also positively related to FA, but this effect was only significant in some of the major white matter tracts. Using a model that included all psychopathic traits/dimensions simultaneously, we found a unique effect of grandiose-manipulative traits. These findings support the notion of the presence of an aberrant white matter microstructure throughout the brain as a neural correlate of grandiose-manipulative and callous unemotional traits in a sample of seriously at-risk juveniles.  In chapter 5 we investigated possible differences in macro- and microstructural brain parameters between a clinical sample of DBD patients and a group of matched healthy controls using both tract-based spatial statistics (TBSS) and voxel-based morphometry (VBM). The study showed smaller grey matter volume accompanied by larger white matter volume and higher FA in the fronto-limbic system of DBD patients compared to healthy controls. Furthermore, we showed higher and lower FA in different parts of the uncinate fasciculus (UF) providing a possible explanation for the inconsistent findings in the literature on FA in the UF in DBD.