This study aimed to investigate the effects of methylphenidate on children with Attention Deficit Hyperactivity Disorder (ADHD). The study employed a conceptual framework of attention, consistent with contemporary theory, and including the following components: sustained attention, selective attention, divided attention, shifting attention, and speed of information processing. Fifteen children (12 boys and 3 girls) of normal intelligence, with a diagnosis of ADHD according to the DSM-IV criteria, and ranging in age from 8 to 11 years participated in the study. Children's attentional abilities were evaluated using the Test of Everyday Attention for Children (TEA-Ch: Manly, Roberston, Anderson, & Nimmo-Smith, 1999). A double-blind counterbalanced repeated-measures design approach was employed to tap on–off medication effects, and deviations from normal. Results showed that comparisons between on–off medication conditions generally detected few differences with respect to sustained and selective attention measures and simple processing speed. In contrast, for higher-level attention domains, including shifting and divided attention, children on medication demonstrated a speed–accuracy trade-off, exhibiting greater accuracy, but slower completion times. When data from the ADHD group were compared to controls a consistent pattern emerged, with children with ADHD in the medication condition being more accurate across all attention domains on all measures. While these children also tended to record slower completion times, group differences and effect sizes were of smaller magnitude. The findings of this study suggest a possible speed–accuracy trade-off effect for children with ADHD on medication.