This thesis is an exploration of values-consistent behaviour from a contextual behavioural science perspective. The first chapter is a systematic review of the effectiveness of acceptance and commitment therapy in enhancing values-consistent behaviour. The results from this review were inconclusive, mainly due to a lack of psychometrically robust outcome measures, and inconsistent use of available measures. Recommendations were made to improve the utility of measures of values-consistent behaviour. The second chapter reports a cross-sectional survey of adolescents, aimed at testing the psychometric properties of values measures, and assessing the relationship between values-consistent behaviour and wellbeing. The measures used in this study were the Valued Living Questionnaire 2 (VLQ-2), Portrait Values Questionnaire – Second Revision, Child and Adolescent Mindfulness Measure, Avoidance and Fusion Questionnaire for Youth – Short Form, and the Warwick-Edinburgh Mental Well-being Scale. Using the VLQ-2 in its current form, values-consistent behaviour was found to account for an additional 13% of variance in wellbeing, above the contributions of demographics, mindfulness and experiential avoidance. However, a recommendation was made for adaptions to be made to the VLQ-2 to make it more suitable for adolescents.