Polydrug using persons pose particular challenges in mental health practice that result from the complexity of cumulative intertwined effects of the addictive course on their cognitive, affective and neurobiological functioning.

To respond to this challenge, this paper presents systematized evidence-based tools developed as part of the multi-site FACE© program (Facilitating Adjustment of Cognitions and Emotions) and analyses how the organization of structured multidimensional assessments impacts on the diagnostic and treatment phases with a series of polydrug and alcohol abusing persons.

At a diagnostic level, practice systematization using a thorough, multidimensional, evidence-based anamnestic protocol appears mandatory to provide the internationally recommended assessment data relevant to designing informed care pathways (cf. World Health Organization, France's ‘Haute Autorité de Santé’, Belgium's ‘Conseil Supérieur de la Santé’). At a treatment level, this protocol reveals beneficial to the practitioner–client relationship, facilitating initiation of a therapeutic contract. Further “assessment to treatment” tools, including monitoring of polydrug use through structured observational agendas and time-line analyses, respond to multiple care challenges by providing both diagnostic and follow-up data. Early treatment course application of psycho-education sessions into self-observational “homework” strategies further benefits comprehension and control of the addiction course by clients.

Evidence-based, structured “assessment to treatment” tools appear to provide valuable insights regarding polydrug use severity, dynamics and contingencies, relevant to initial multidisciplinary assessment and treatment course evaluation. Significantly, these are also found to ameliorate addiction insight along with facilitating cognitive-emotional regulation by the client. Further research and practice implications are advocated.