Dual diagnosis is well recognized as a significant clinical problem. It is associated with poor outcomes, staff difficulties, and management problems. This exploratory study investigated the extent and clinical correlates of dual diagnosis and traditional substance use among the mentally ill by interviewing staff from several substance misuse and mental health services in Northern India, using a semi-structured interview schedule and focus groups. Dual diagnosis was seen as a common problem according to staff interviewed from substance misuse and mental health services, although types of substance use reported were different than in western studies. Traditional substance use (the use of substances in distinct cultural, religious, and social settings that is not prohibited, such as khat or betel nut) also was reported as common among those with dual diagnosis. Substance misuse among the mentally ill is common in Northern India. Opportunities exist for informing mental health nursing practice about "traditional" substance use.