Regarding the effects of Mindfulness Based Interventions (MBIs) on adolescents, the field has rarely moved beyond early stage evaluations. According to a recent meta-analysis, there are only a small amount of randomized controlled trials evaluating the effects of MBIs on outcomes such as mental health, social behaviour, executive functions and attention. Only a third of studies included in this meta-analysis include mindfulness as an outcome. It is of high importance, however, to study mindfulness skills as potential mechanisms of change in MBIs to better understand how MBIs exert their effects on the different outcome categories. This can ultimately help to improve current MBIs for adolescents. To be able to reliably and validly measure mindfulness in adolescents, a well-validated questionnaire that covers all aspects of the multi-factor construct is crucial. However, most of the available self-report questionnaires for youth are only single factor measures. The 37-item Comprehensive Inventory of ...