The present study aimed to explore the motivations that lead adolescents to engage in deliberate self-harm. It also sought to examine the relationship between body image, timing of puberty and deliberate self-harm in clinical and non-clinical adolescent populations. The research design employed was a cross-sectional survey of the two identified populations, using both standardised and non-standardised questionnaires. The design utilised both between and within subject measures to examine the relationships across a number of different variables. 218 participants took part in the study. 21 were from a clinical population and 197 were recruited through local schools. Data were collected using questionnaire measures (Hospital Anxiety and Depression Scale; Body Dysmorphic Disorder Questionnaire; Emotion Regulation Questionnaire; Self-Harm Innovatory; Self-Injury Motivation Scale –II). Results found significantly higher levels of psychopathology, body image concerns and dysfunctional emotion regulation strategies in those who self-harmed. Rates were higher among the clinical self-harm group than the non-clinical self-harm group. In addition, worry about body image, experiences of being bullied and dysfunctional emotion regulation strategies were found to be better predictors of self-harm than other variables considered. Timing of puberty was not found to correlate significantly with self-harm. No differences were found in motivations for self-harm between clinical and non-clinical populations. Results support previous findings that body image is a risk factor for self-harm, that those with higher levels of psychopathology are more likely to harm, and that dysfunctional emotion regulation strategies are correlated with self-harm.