Large overjet has been associated with an increased risk of trauma of the permanent maxillary incisors, especially before 10 years of age. The prevalence of an overjet of more than 6 mm in 10-year-old Swedish children is about 15%. To prevent trauma by reducing the overjet, this treatment be set in early in life. However, compliance with orthodontic treatment is a significant and well known problem and may be associated with the age of the patient. This study concerns children treated with an open activator with built in headgear (HG activator). The aim of treatment was to reduce the trauma risk in these patients as early as possible, and an objective of the study was to gain better knowledge of young children's (6-13 years of age) motivation for and response to correction of large overjet. In-depth interviews focusing on motivation were held with 18 children. Interviews were transcribed verbatim and analysed according to Grounded Theory, a qualitative method. The results indicate the importance of parental involvement for younger children's compliance. Older children seem to have a higher degree of internal motivation for treatment and less need for parental support for compliance with treatment. If treatment compliance can not be ensured through parents' wholehearted involvement and control it seems to be better to delay treatment until the child is older.