The definition "Dual Diagnosis" leads to the dangerous pitfall of understanding two distinct pathological elements and suggests to addiction and psychiatry specialists a non-interconnected approach.Therefore, we prefer to use the term comorbidity DUS and psychiatric disorder.This condition is increasingly common in clinical settings, especially within the prison setting.In this environment, clinical pictures are more complex because of the difficulties inherent in the inmate’s life, the complications related to the proper use of psychotropic drugs, and the different instances that gravitate around the diagnostic and certification processes.A diagnostic pathway that determines the temporality of the two disorders, clarifying the mutual influences, is essential; the use of objective diagnostic tools such as toxicological examinations and psychic tests is useful.Treatment must involve bringing to bear the knowledge and opportunities available to the field of Addiction and Psychiatry, with the cultural and operational rigidities of the two fields being overcome.In the treatment processes on comorbid inmates, a continuous relationship with external specialist services is necessary to create the conditions for the continuum of care.