Psychological approaches may be both more cost-effective and have less negative health-related and environmental impacts than drugs in helping children to relax and reduce pain during medical interventions. There is a lack of knowledge concerning how children’s experience, gender, background and socio-economic factors may influence their experience of interactive visualization. This paper presents a user-centered design project where the aim is to develop knowledge concerning the effect that visualization used as pain-relieving intervention in medical procedures has on children. The target group is children undergoing medical procedures.