Background: Most research explores the impact of digital technology, specifically social networking sites, on mental health and wellbeing amongst adolescents. Findings suggest small effects with a possible link amongst girls. This investigates whether levels of mental health and wellbeing impact use of digital technology amongst adolescents. Methods: Data come from waves 1-9 of Understanding Society: The UK Household Longitudinal Study, a longitudinal panel study with a youth panel (10-15 year olds) where household members are interviewed annually. Young people were asked about time spent using social networking sites, and gaming on a console or computer. Measures of mental health and wellbeing were the Strengths and Difficulties Questionnaire and a composite happiness measure. Random effects ordinal logistic models were used to test associations. Findings: Higher levels of happiness and lower levels of poor mental health were associated with lower levels of digital technology use. Slightly larger associations were observed amongst girls for social networking site use and amongst boys for console gaming. There were no gender differences in the association between levels of mental health and wellbeing and time spent playing computer games. Happiness with family was associated with social networking site use for girls while happiness with friends was associated for boys. Internalising behaviours showed associations across all types of digital technology with higher levels of internalising associated with increased time on digital technology. Interpretation: The findings of this study suggest that there is a relationship between existing mental ill health and increased use of digital technology for adolescents. There also appear to be certain aspects of these measures which may be important, particularly internalising behaviours. Future studies should explore the pathways of these relationships to identify characteristics of vulnerable young people and to inform policy and decisions of parents and young people in their use of digital technology. Funding Information: YK was supported by the Economic and Social Research Council (ESRC ES/R008930/1); CB was supported by (ESRC RES-586-47-0001/RES-586-47-0002). Understanding Society is funded through the following ESRC grants: Understanding Society: The UK Longitudinal Household Study (RES-586-47-0001); Understanding Society, the UK Longitudinal Studies Centre (RES-586-47-0002). The ESRC provided funding for the collection of UKHLS data; however they were not involved in the study design, analysis, interpretation of the data or writing up of this paper. Declaration of Interests: The authors declare no conflicts of interest. Ethics Approval Statement: Parents or guardians provides consent for young people to participate. Young people are then asked for assent for a pen-and-paper questionnaire. The University of Essex Ethics Committee has approved all data collection on Understanding Society main study and innovation panel waves, including asking consent for all data linkages except to health records. Requesting consent for health record linkage was approved at Wave 1 by the National Research Ethics Service (NRES) Oxfordshire REC A (08/H0604/124), at BHPS Wave 18 by the NRES Royal Free Hospital & Medical School (08/H0720/60) and at Wave 4 by NRES Southampton REC A (11/SC/0274). Approval for the collection of biosocial data by trained nurses in Waves 2 and 3 of the main survey was obtained from the National Research Ethics Service (Understanding Society - UK Household Longitudinal Study: A Biosocial Component, Oxfordshire A REC, Reference: 10/H0604/2).