This study examined whether girls and boys with ADHD show similar impairments in cognitive control from childhood into adolescence and the developmental relationship between cognitive control and ADHD symptoms. Participants include 8–17-year-old children with ADHD (n = 353, 104 girls) and typically developing (TD) controls (n = 241, 86 girls) with longitudinal data obtained from n = 137. Participants completed two go/no-go (GNG) tasks that varied in working memory demand. Linear mixed-effects models were applied to compare age-related changes in cognitive control for each GNG task among girls and boys with ADHD and TD controls and in relation to ADHD symptoms. Boys with ADHD showed impaired response inhibition and increased response variability across tasks. In contrast, girls with ADHD showed impaired response inhibition only with greater working memory demands whereas they displayed increased response variability regardless of working memory demands. Analysis of age-related change revealed that deficits in cognitive control under minimal working memory demands increase with age among girls with ADHD and decrease with age among boys with ADHD. In contrast, deficits in cognitive control with greater working memory demands decrease with age among both boys and girls with ADHD compared to TD peers. Among children with ADHD poor response inhibition during childhood predicted inattentive symptoms in adolescence and was associated with less age-related improvement in inattentive symptoms. These findings suggest that girls and boys with ADHD show differential impairment in cognitive control across development and response inhibition in childhood may be an important predictor of ADHD symptoms in adolescence.