It is important to keep in mind that VR is not really a treatment in itself; rather, VR is a new technological instrument that can be applied for therapeutic purposes. But the success of VR systems in this aspect will depend very much on how familiar designers and developers are with concepts of motor control and learning as well as specific needs of the clinical population. This understanding is a key factor to designing appropriate therapeutic systems for successful implementations in rehabilitation settings. In addition, considerable engineering skills as well as knowledge about human-computer interaction is required to understand the potential capabilities of various technologies and to make the most of it in suitable applications. Thus, to achieve successful results, work within this area require collaborative efforts in an interdisciplinary team (e.g. physiotherapy, informatics, and engineering) Equally important is that children (the target group) and parents participate in the process as they are the real experts in the area.4, 144 The projects that form the basis of this thesis has been conducted in close collaboration with the Department of Informatics and to some extent with engineers and psychologists