Background: Internet Gaming Disorder (IGD) and Gaming Disorder (GD) have emerged as significant public health concerns, with studies highlighting their association with substance use. Research on IGD/GD faces challenges due to heterogeneous definitions and measurement tools. While the introduction of DSM-5 and ICD-11 criteria for these behaviors improved research consistency, substance use patterns in individuals with IGD/GD, when defined strictly by these criteria, remain unexplored. Importantly, a comprehensive review of substance use patterns among individuals with IGD/GD based on DSM-5 and ICD-11 criteria has never been conducted. Objective: This scoping review aims to map existing literature on substance use in individuals with IGD/GD, focusing on patterns, underlying mechanisms, and moderating factors influencing this relationship. Methods: The review adhered to the JBI manual for scoping reviews and PRISMA-ScR standards. A literature search was conducted in August 2025, in seven bibliographic databases, supplemented by citation tracking strategies. Inclusion criteria encompassed empirical studies published post-2013, using scales published after 2013, based on DSM-5/ICD-11 criteria for IGD/GD, and focusing on substance use. Results: A total of 36 studies out of 5,561 identified, predominantly cross-sectional, were included. Findings indicated a high co-occurrence of IGD/GD and substance use, particularly among adolescents and young adults. Shared risk factors such as impulsivity, sensation-seeking, and maladaptive coping strategies were identified. Alcohol, tobacco, stimulants, and cannabis emerged as the most commonly used substances, with variations across cultural contexts. Limited longitudinal data underscored the need for research on the progression and interaction of IGD/GD and substance use over time. Conclusion: The findings revealed that individuals with IGD/GD frequently engage in substance use, including alcohol, tobacco, cannabis, and stimulants such as amphetamines. This review highlights critical mechanisms linking IGD/GD and substance use, emphasizing the role of behavioral reinforcement and emotional dysregulation. Future research should focus on longitudinal designs and protective factors to inform tailored prevention and intervention strategies. Systematic screening for substance use is warranted among individuals with IGD/GD.  Kulcsszavak: internet gaming disorder, substance use, behavioral addiction, scoping review