The main objective of this study was to evaluate the variables influencing the efficacy of different approaches to addressing the problem of drug use among juvenile offenders. A longitudinal study was conducted with 79 adolescent internees at the Teresa de Calcuta CEMJ (Centro de Ejecución de Medidas Judiciales) in Madrid. Therapeutic interventions were conducted with adolescents with severe drug-related problems. For data analysis, binary logistic regression analysis was used. Therapeutic success after a three-month follow-up period was 53.2%. The regression analysis correctly classified 86.1% of the cases, effectively predicting 85.7% of therapeutic success and 86.5% of therapeutic failure. The analysis identified 4 predictive factors: the number of criminal charges resulting in internment, number of minor infractions committed during detention, prior consumption of ecstasy and risk factors in personality and/or behavioural issues. The results suggest that judicial and therapeutic interventions should be based on the chronicity of delinquency and other individual personality traits.