Objective: The main aim of the present study was to consider the impact of gaming motivations among young adults when evaluating the relationship between probable attention deficit hyperactivity disorder (ADHD) and massively multiplayer online role-playing games (MMORPGs), with disordered gaming. Method: In the present study, participants were assessed with the Adult ADHD Self-Report Scales (ASRS-v1.1), the Motives for Online Gaming Questionnaire (MOGQ), and the nine-item Internet Gaming Disorder Scale-Short Form (IGDS9-SF). Results: Participants with probable ADHD (n=143, 19.2%) and without probable ADHD (n=602, 80.8%) did not differ according to the current age, gender, presence of romantic relationship, marital status, where and with whom they are living, employment status and time spent on the gaming. Compared to participants without probable ADHD, those with probable ADHD had higher rates of having a game console, purchasing games, gaming more than usual on weekends, having problems related to gaming, probable internet gaming disorder (IGD) according to IGDS9-SF cut-off score and higher scales scores (IGDS9-SF and MOGQ), whereas they had a lower age at first gaming. Among different game types, those with probable ADHD were gaming more with multiplayer online battle arena games, social network games, music games, MMORPGs, sports games/car games, and horror-themed/survival games. Scores of all six types of gaming motives were higher among those with probable ADHD, and among them coping/escape, social, skill development, and fantasy distinguished the presence of probable ADHD. In the ANCOVA analysis, the presence of probable ADHD and the use of MMORPGs (as well as online gaming motives [coping/escape, recreation, fantasy, social and competition]) predicted the severity of IGD symptoms, and also these effects also interacted, involving probable ADHD and using MMORPGs. Conclusion: These findings suggest that those with probable ADHD may have different gaming characteristics than those without probable ADHD. Probable ADHD and using MMORPGs are related to the severity of disordered gaming, along with almost all type of online gaming motivations. Also, the effects of probable ADHD and MMORPGs use interacted with each other.