Introduction: The American Psychiatric Association introduced in Internet Gaming Disorder (IGD) in the appendix as a tentative disorder in the last edition of the Diagnostic and Statistical Manual of Mental Disorders. However, currently no systematic review exists about excessive gaming viewed from a clinical perspective. Objectives and aims: To review clinical studies on gaming addiction in order to ascertain characteristics of both clinical and research studies to provide retrospective evidence in relation with the proposed IGD classification (including criteria, measures and therapies). Methods: A systematic literature review of studies published from 1980 to 2015 has been conducted using three major psychology databases: Academic Search Complete, PsycInfo, and PsycArticles. A total of 5033 results from peer-reviewed journals were obtained, where 32 were identified as empirical clinical papers focused on gaming addiction. Results: The clinical research studies on gaming identified were published between 1998 and 2015, most of which included patient samples. Categorizations identified in the research papers included: (i) patients’ characteristics (e.g., socio-demographics), (ii) criteria and measures used (e.g., scales to diagnose), (iii) types of gaming problems (e.g., game genre), (iv) and treatments (e.g., type of therapy). Conclusions: Findings will be discussed against the background of the controversial IGD diagnostic criteria proposed in the DSM-5 in order to assess the extent to which previously published clinical knowledge matched the current proposal for including gaming addiction as behavioral addiction in the next diagnostic manual.