Co-occurring substance use and mental health disorders (CODs) are common. However, very little is known about individuals' recognition of, and perception of the relationship between these disorders. The current study aimed to examine problem recognition, perceived disorder relationships, treatment intentions, and treatment preferences of individuals attending Australian detoxification facilities. Questionnaires were completed by 225 participants, including the Mental Health Screening Form III and the Treatment Preferences Questionnaire. Results indicated that 56.4% of participants screened positive for CODs, with only 4.2% failing to recognise their mental health problems. Participants perceived a functional relationship between disorders, where improvement/deterioration of one disorder leads to the improvement/deterioration of the other. Recognition of mental health problems and perception of a functional relationship between disorders, predict high mental health treatment intentions. These findings have important clinical implications when planning treatment programs and counselling individuals with CODs.