Dual diagnosis (DD) commonly identifies a condition of co-occurrence of substance use disorders and psychological or psychiatric disorders. Many scholars have tried to explain this phenomenon, yet no agreement has been found: methodologies of intervention and treatment are numerous, but there is no uniformity of methodology. Our work aims to search critical aspects linked to this fragmented framework, to facilitate those who use the construct of DD. We have elaborated a literary review focused on specific critical contributions to the theoretical and methodological complexity of the construct. Scopus, PubMed, and Scholar were used as search engines. Our research reveals significant problems around several thematic areas: Defining, Operative and Treatment; Economic and Policy; Pharmacological Approach; and Patients' Perspectives Issues. Consistent issues are discussed with regard to DD: innovation should start from its limits. Future research should look for alternative theoretical formulations and consequent intervention experiences to provide new perspectives.