Aim: This study evaluated the consistency between the International Classification of Diseases, 11th Edition (ICD-11) for gaming disorder (ICD-11-GD) and Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for internet gaming disorder (DSM-5-IGD). Moreover, the functional impairment of participants and their insight of their GD were evaluated. Methods: We recruited 60 participants with GD, 45 participants who engaged in hazardous gaming (HG), and 120 controls based on a diagnostic interview. Their operationalization of functional impairment and stage of change were evaluated by interviews and questionnaires, including the Brief Gaming Negative Consequence Scale (BGNCS). Results: We observed satisfactory consistency (kappa value 5 0.80) with a diagnostic accuracy of 91.5% between the ICD-11-GD and DSM-5-IGD criteria. Furthermore, 16 participants with IGD in DSM-5 were determined to have HG based on the ICD-11 criteria. Participants of GD group experienced impaired functioning in their health (96.7%), career (73.3%), social life (61.6%), academic performance (36.7%), and job performance (35%). Moreover, a proportion of them were in the pre-contemplation (25.0%), contemplation (61.7%), preparation (10%), and action stages (3.3%). Conclusion: There is a good consistency between ICD-11-GD and DSM-5-IGD criteria. The ICD-11 criteria have a high threshold for diagnosing GD. HG criteria could compensate for this high threshold and identify individuals with a gaming-related functional impairment who require help. Most of the participants with GD were in the early stage of change. Interventions to promote their insight are essential. The BGNCS can be used to examine the negative consequences of gaming and aid mental health professionals in assessing functional impairment. Kulcsszavak: gaming disorder, hazardous gaming, ICD-11, functional impairment, stage of change, insight