<p>Selectively focusing on relevant information while filtering out irrelevant inputs seems to be a simple part of life; however, it can be challenging for children with attention deficit hyperactivity disorder (ADHD). Using multivariate pattern analysis (MVPA) of electroencephalogram (EEG) data, we aimed to investigate the neurophysiologic basis of auditory selective attention deficits in children with ADHD. EEGs were recorded from typically developing (TD) children (<i>n</i> = 92) and children with ADHD (<i>n</i> = 93) while they performed an auditory oddball task. In terms of both sound categorization and localization decoding, children with ADHD exhibited a significant delay in distinguishing between target and nontarget sounds when compared with TD children, reflecting deficits in early-stage auditory attention processing. Importantly, children with ADHD exhibited reduced decoding accuracy for target localization but increased decoding accuracy for nontarget localization, indicating their deficits in focusing on relevant sound while failing to adequately inhibit irrelevant information. Additionally, the impaired early-stage target localization in children with ADHD predicted greater response variability and inattentive symptom severity. Our findings provide insight into the neural mechanisms of auditory selective attention impairments in children with ADHD, highlighting the dual deficits of target selection and nontarget inhibition.</p> Graphical Abstract <p></p>