Aims: This study aimed to explore the brain activity characteristics of individuals with Internet Gaming Disorder (IGD) during mobile gameplay, focusing on neural responses to positive and negative game events. The findings may enhance our understanding of the neural mechanisms underlying IGD. Methods: Functional near-infrared spectroscopy (fNIRS) was employed to measure hemodynamic responses (HbO/HbR) in the prefrontal cortex of both IGD participants and recreational gaming users (RGU), during solo and multiplayer mobile gameplay. Results: In solo mode, IGD participants exhibited stronger activation in the dorsolateral prefrontal cortex (dLPFC), frontopolar area (FPA), orbitofrontal cortex (OFC) in response to positive events compared to RGU. Negative events led to reduced activation in the FPA among IGD participants. In multiplayer mode, IGD participants displayed lower activation in the dLPFC and ventrolateral prefrontal cortex (vLPFC), although overall brain response trends to positive and negative events were similar between IGD and RGU. Conclusions: This study suggests that individuals with IGD exhibit heightened sensitivity to rewards and diminished sensitivity to losses, along with potential impairments in the executive control network. These results contribute to a better understanding of the neural mechanisms of IGD and offer insights for developing targeted interventions aimed at addressing abnormal reward and loss processing.  Kulcsszavak: Internet Gaming Disorder, recreational gaming users, reward/loss processing, prefrontal cortex