Issues. Comorbidity between anxiety and substance use disorders is common, yet it is poorly understood and poorly treated.Approach. Narrative literature review. PsycINFO Research on psychological interventions for comorbid substance and mental disorders should address specific comorbid relationships, test specific models of comorbidity, examine processes that underlie or maintain comorbidity, and test interventions that target likely maintaining processes. Furthermore, as comorbidity is the norm rather than the exception in clinical samples, research on single disorders will lack generalisability unless it addresses comorbidity. Comorbidity between substance use and other mental disorders can include heterogeneous and complex combinations of problems that may need to be grouped into those with similar features for intervention to be successful.In many cases there is good evidence from preclinical [1] and epidemiological [2] research that substance use and anxiety disorders have a reciprocal relationship. The nature of the relationship between comorbid disorders provides a rationale for sequential, parallel or integrated treatment of the comorbidity [3]. Where comorbid disorders show a reciprocal relationship successful treatment should then target not just the specific disorders but the relationship between the disorders in an integrated fashion. However, clinical trial evidence suggests at best that treatment for specific disorders leads to outcomes for that disorder and not the other [4,5].