To examine gender differences in the co-occurrence of DSM-III-R axis I disorders and axis II personality disorders in young adult psychiatric inpatients with substance use disorders (SUDs), a consecutive series of 70 inpatients (33 men and 37 women) with SUD were reliably assessed with structured diagnostic interviews. Higher rates of dysthymia and eating disorders were observed in SUD females and higher rates of cluster A personality disorders were observed in SUD males. No gender differences were found for depression or anxiety in our SUD inpatients; these findings contrast with gender ratios for these disorders in the general population. In conclusion, relatively few gender differences were found in young adult inpatients with SUD, even where they would be expected based on general population gender patterns.