Purpose -The term ''dual diagnosis'' has been widely accepted as referring to co-existing mental illness and substance misuse. However, it is clear from the literature that individuals with these co-existing difficulties continue to be excluded from mainstream mental health services. The term ''dual diagnosis'' can be pejorative and therefore, complicate or obstruct engagement. It is argued within this paper that the association between mental illness and substance misuse (including alcohol misuse) is an intricate and often a complex relationship involving a multitude of psychosocial factors that cannot be simply explained by an individual having two co-existing disorders. From this perspective, this paper seeks to argue that the term ''dual diagnosis'' should be actively de-emphasised.Design/methodology/approach -This paper offers a critique of ''dual diagnosis'' and the potential impact on access and treatment through discussion of the literature and reflections on service provision.Findings -The paper identifies five principles termed the ''5 key principles'', which support individuals with a wide spectrum of co-existing difficulties and to counteract the stigma often associated with the term ''dual diagnosis''. These collective principles allow the practitioner to consider the needs of the service user from the service user's perspective and therefore not be distracted by the perceived set of expected behaviours that are implied by the ''dual diagnosis'' label.Originality/value -This paper offers a critique of the term ''dual diagnosis'' and explores the impact of this in terms of service users and makes practical suggestions for alternative ways of conceptualising co-existing mental health and substance difficulties.