OBJECTIVE To investigate in a community sample the association of suicide-related cognitions and behaviors ("thoughts of death", "desire for death", "suicidal thoughts", and "suicidal attempts") with the comorbidity of depressive disorders (major depressive episode or dysthymia) and alcohol or substance use disorders. METHOD The sample was 1464 subjects interviewed in their homes using the Composite International Diagnostic Interview to generate DSM-III-R diagnosis. Descriptive statistics depicted the prevalence of suicide-related cognitions and behaviors by socio-demographic variables and diagnoses considered (major depressive episode, dysthymia, alcohol or substance use disorders). We performed a multivariate logistic regression analysis to estimate the effect of comorbid major depressive episode/dysthymia and alcohol or substance use disorders on each of the suicide-related cognitions and behaviors. RESULTS The presence of major depressive episode and dysthymia was significantly associated with suicide-related cognitions and behaviors. In the regression models, suicide-related cognitions and behaviors were predicted by major depressive episode (OR=range 2.3-9.2) and dysthymia (OR=range 5.1-32.6), even in the presence of alcohol use disorders (OR=range 2.3-4.0) or alcohol or substance use disorders (OR=range 2.7-2.8). The interaction effect was observed between major depressive episode and alcohol use disorders, as well as between dysthymia and gender. Substance use disorders were excluded from most of the models. CONCLUSION Presence of major depressive episode and dysthymia influences suicide-related cognitions and behaviors, independently of the presence of alcohol or substance use disorders. However, alcohol use disorders and gender interact with depressive disorders, displaying a differential effect on suicide-related cognitions and behaviors.