Substance abuse treatment outcome studies have shown positive effects for a large number of drug users with regard to reduction in substance use and criminal activity, as well as improvement of general well-being. However, high rates of relapse following treatment have compelled researchers to elucidate the individual difference factors that change among those who receive substance abuse treatment. Affect- (depressive and anxiety symptoms) and disinhibition-related variables (impulsivity, risk taking) may be of particular relevance. These factors are related to the development and maintenance of substance use and distinguish between substance users with and without Axis I and II disorders that may interfere with treatment success, such as depression, anxiety disorders, or antisocial personality disorder. Consequently, these factors may be considered important treatment targets. However, there currently is a dearth of research focused on understanding whether these variables are affected by standard substance use treatments, and more specifically, which variables may change throughout the course of substance use treatment. Given that many of these variables are considered to be enduring aspects of an individual's personality, the extent to which they are malleable by treatment is an important consideration. Moreover, to enhance the generalizability of these findings, it is important to understand the extent to which changes occur in more standard substance use treatments as opposed to more elaborate and targeted treatments that rarely are disseminated in real world treatment settings. Therefore, the purpose of the current study was to examine the effect of a residential substance use treatment program on particular affect- (e.g., depressive and anxiety symptoms, stress reactivity) and disinhibition-related variables (e.g., risk taking). A sample of 81 inner-city substance abusers were assessed on self-reported and behavioral measures of the above affect- and disinhibition-related variables that have previously found to be implicated in substance use over a 30-day course of treatment. A residential treatment program provides an optimal setting for evaluating changes as behavioral confounds (i.e., substance use) can be controlled, and the natural changes during abstinence can be measured with both reliability and validity. A significant pre-post treatment decrease was found on scores of risk taking, as indexed by the Balloon Analogue Risk Task (BART); levels of depressive symptomatology and stress reactivity also evidenced a significant pre-post decrease. These data are discussed with respect to implications for understanding the factors that underlie mechanisms of change during treatment, thereby informing substance abuse prevention and treatment programs.