Acquired brain injury (e.g., traumatic brain injury, brain tumour, brain infections) is one of the leading causes of death and disability for children and adolescents. Importantly, injuries affecting the brain in childhood or adolescence appear during a time of development when the brain is particularly vulnerable. Thus, pediatric acquired brain injury does not only impact cognitive functions at the time of injury or onset of disease, but also cognitive functions that are yet to develop. Changes in cognitive function, and in particular executive dysfunction due to acquired brain injury, cause significant real-life disability, yet solid evidence in support of executive functioning interventions for children and adolescents is lacking. In the present study different group-based cognitive rehabilitation interventions will be compared. The aim of the study is to investigate if a group-based "brain training" intervention is able to improve executive function in children and adolescents after acquired brain injury. Efficacy will be assessed immediately after intervention, but also six months after the intervention. The project is in line with international research efforts aimed at establishing more knowledge about how children and adolescents with brain injuries respond to cognitive rehabilitation.