Many people with substance use disorders are vulnerable to other psychiatric disorders and present to addiction treatment services with comorbid psychiatric symptoms. To describe the prevalence of recent psychiatric treatment and current psychiatric symptoms and explore links between substance misuse, personal/social functioning and symptom severity. Subjects were 1075 adults recruited to the National Treatment Outcome Research Study (NTORS), of whom 90% were opiate-dependent. Psychiatric symptoms at intake were recorded using sub-scales from the Brief Symptom Inventory. Recent psychiatric treatment was reported by one in five subjects. Psychiatric symptom levels were high and females had elevated scores on all scales. Symptoms were elevated among opiate users who were also frequent users of benzodiazepines, alcohol and, in particular, stimulants. Gender, physical health, drug dependence and personal relationship problems were more powerful predictors of psychiatric symptoms than substance use. Addictions service providers should be vigilant to psychiatric problems among their clients at intake to treatment. Psychiatric symptoms are more closely linked to polydrug use than to opiate use in this population.