Specific psychiatric diagnoses and comorbidity patterns were examined to determine if they were related to the medical lethality of "suicide attempts" among adolescents presenting to an urban general hospital (N = 375). Bivariate analysis showed that attempters with substance abuse disorders had higher levels of lethality than attempters without substance abuse. Regression results indicated having depression comorbid with any other diagnosis was not associated with medical lethality. However, having a substance abuse disorder was associated with higher suicide attempt lethality, highlighting the importance of substance abuse as a risk factor for lethal "suicide attempts" in adolescents. This finding stimulates critical thinking around the understanding of suicidal behavior in youth and the development and implementation of treatment strategies for suicidal adolescents with substance abuse disorders. (Contains 1 table.)