This study tested the specificity of parent alcoholism effects on young adult alcohol and drug abuse/dependence, anxiety, and depression, and tested whether adolescent symptomatology and substance use mediated parent alcoholism effects. Participants were from a longitudinal study in which a target child was assessed in adolescence and young adulthood with structured interview measures (N = 454 families at Time 1). Results showed unique effects of parent alcoholism on young adult substance abuse/dependence diagnoses over and above the effects of other parental psychopathology. There was some evidence of parent alcoholism effects on young adult depression and of maternal alcoholism effects on young adult anxiety, although these were not found consistently across subsamples. Mediational models suggested that parent alcoholism effects could be partially (but not totally) explained by adolescent externalizing symptoms.