Sustained attention is a fundamental cognitive ability that influences various aspects of human functioning. Studies of the neural correlates of attention commonly treat sustained attention as an isolated construct, however in any ecological context, sustained attention interacts with other executive functions such as inhibition of interference and processing of complex hierarchical stimuli. We have thus constructed a protocol to probe the interplay between these cognitive processes during visual attention task. We contrast putative typical vs atypical attention by comparing 18 healthy participants with 53 adults with Attention-Deficit/Hyperactivity Disorder, for whom difficulties with sustained attention are a core symptom and thus constitute a natural experiment condition. Our behavioural and brain-imaging analyses demonstrate distinct neural patterns in bottom-up visual processing and attention allocation mechanisms in ADHD and Control groups, highlighting different cognitive strategies utilised by adults with ADHD and healthy participants in tasks requiring sustained attention.