This meta-analysis of 55 functional MRI (fMRI) studies examines the neural correlates of Attention-Deficit/Hyperactivity Disorder (ADHD). The study searched multiple databases for studies published up to June 30, 2011, and included significant differences in brain region activation between individuals with ADHD and controls using activation likelihood estimation meta-analysis (p<0.05, corrected). The analysis focused on age groups (children and adults), clinical characteristics (history of stimulant treatment, presence of comorbidities), and specific neuropsychological tasks (inhibition, working memory, vigilance/attention). In children, hypoactivation was found in executive function and attention networks, while hyperactivation was observed in default, ventral attention, and somatomotor networks. In adults, hypoactivation was predominantly in the frontoparietal system, and hyperactivation was in visual, dorsal attention, and default networks. The findings suggest that ADHD-related dysfunction involves multiple neuronal systems, including higher-level cognitive functions and sensorimotor processes, and are not fully explained by comorbid mental disorders or stimulant treatment history. The results support a systems neuroscience perspective on ADHD, emphasizing the importance of large-scale neural network dysfunctions.This meta-analysis of 55 functional MRI (fMRI) studies examines the neural correlates of Attention-Deficit/Hyperactivity Disorder (ADHD). The study searched multiple databases for studies published up to June 30, 2011, and included significant differences in brain region activation between individuals with ADHD and controls using activation likelihood estimation meta-analysis (p<0.05, corrected). The analysis focused on age groups (children and adults), clinical characteristics (history of stimulant treatment, presence of comorbidities), and specific neuropsychological tasks (inhibition, working memory, vigilance/attention). In children, hypoactivation was found in executive function and attention networks, while hyperactivation was observed in default, ventral attention, and somatomotor networks. In adults, hypoactivation was predominantly in the frontoparietal system, and hyperactivation was in visual, dorsal attention, and default networks. The findings suggest that ADHD-related dysfunction involves multiple neuronal systems, including higher-level cognitive functions and sensorimotor processes, and are not fully explained by comorbid mental disorders or stimulant treatment history. The results support a systems neuroscience perspective on ADHD, emphasizing the importance of large-scale neural network dysfunctions.