This study aimed to examine (a) the impact of the change in the "Diagnostic and Statistical Manual of Mental Disorders" ("DSM") from a categorical to dimensional classification of substance use diagnoses, (b) the elimination of the legal criterion, and (c) the inclusion of a craving criterion in the "DSM"-5. Specifically, we aimed to compare the differential diagnostic outcomes among high-risk substance-using adolescents enrolled in a school-based Motivational Enhancement Therapy (MET) intervention. We explored the alterations of diagnoses of adolescents in this sample and the prevalence of diagnostic promotions and demotions. We hypothesized that the dimensional approach of the "DSM"-5 would improve the utility of diagnosis in predicting severity of consequences and treatment outcomes in our sample. Method: Participants included 273 adolescents enrolled in a school-based intervention and were primarily male (76%) and Caucasian (47%), with 17% Asian/Pacific Islander, 17% Hispanic, 7% African-American, and 1% American Indian/Alaska Native. Results: We found that adolescents who lost diagnoses in the "DSM"-5 generally used substances less frequently and had fewer non-diagnostic negative consequences than those who remained consistently diagnosed across systems. Those who gained a diagnosis via the dimensional system tended to show higher use patterns and have more negative consequences than those who were never diagnosed. These findings indicate that the changes in the "DSM" are appropriate in this school-based clinical sample, at least in matching diagnostic status with substance use topography and negative consequences.