Psychosocial differences between criminal-justice-referred and voluntary clients, using a sample of 996 men and women in residential drug treatment in northern New Jersey, were explored. Results suggest differences in demographic characteristics between the two groups as well as differences in attitudes and behaviors likely to impact on treatment outcome. Demographically, criminal-justice clients are younger, more likely to be male, and less likely to be Black than other clients. They also report better health status and better social and psychological adjustment, reporting less homelessness, fewer health problems, lower levels of psychological distress, better family adjustment, and fewer medical, social, and drug problems requiring intervention. Implications for treatment are discussed.