Introduction: Although substance abuse is an important clinical problem in schizophrenic patients, very little evidence explains why these patients use drugs and alcohol. This study therefore aimed to examine whether premorbid personality disorders affect substance abuse. Methods: The sample included 40 male schizophrenic patients with and 40 male schizophrenic patients without substance use disorder comorbidity who had applied to Ankara Numune Research and Training Hospital. Each participant and a family member were interviewed in a structured clinical interview that addressed premorbid personality disorders. Results: Altogether, 32 patients (80%) in the group with comorbidity and 28 (70%) in the group without comorbidity had a premorbid personality disorder. Antisocial (35% vs. 0%; p<.001) and borderline (37.5% vs. 5%; p=.001) personality disorders were more often detected in the group with comorbidity, while avoidant (10% vs. 35%; p=.014) and obsessive-compulsive (0% vs. 15%; p=.026) personality disorders were less frequently found in this group. Comparing the group with comorbidity with premorbid personality types, schizophrenic patients with premorbid antisocial personality disorder were more frequently unemployed and hospitalized as well as had an earlier onset age of schizophrenia (p=.034, p=.038 and p=.035, respectively). Schizophrenic patients with premorbid borderline personality disorder had a significantly earlier onset age of substance use (19 +/- 5; p=.028). Conclusion: Schizophrenic patients with substance use comorbidity variously differ from those without comorbidity and some of these differences may be associated with premorbid personality disorders.