A co-existence of chemical dependence and other psychiatric syndromes is commonly referred to as “dual-diagnosis.” This categorization is commonly made by social workers in several European countries assigned the primary responsibility for the care of drug and alcohol dependence. Here, we examined the validity of this categorization through systematic, structured patient evaluation following a minimum of 3 weeks of abstinence from drugs and alcohol. Less than one-third of patients originally labelled as suffering from “dual-diagnosis” by the social services did in fact obtain any Axis I DSM IIIR diagnosis, and less than half of the patients had any psychiatric diagnosis other than dependence. Syndromes commonly discussed in the context of self-medication, i.e., unipolar depression and anxiety syndromes, were not over-represented compared to a population sample, while chronic psychoses and bipolar syndromes were highly significantly more common. We conclude that the dual-diagnosis concept, unless substantiated through stringent diagnostic procedures by psychiatrically trained personnel, may be of questionable utility in caring for patients presenting with psychiatric symptoms and substance dependence. A systematic individual evaluation in an alcohol- and drug-free state of sufficient duration is necessary to obtain a basis for an adequate individual treatment plan.