This study examined developmental differences in, and cognitive bases of, coping flexibility in children with and without ADHD. Younger (age 7 to 8) and older (age 10 to 11) children with and without ADHD (N = 80) responded to hypothetical vignettes about problematic interactions with peers that shifted from controllable to uncontrollable over time. We assessed children's coping strategies, perceptions of controllability, coping repertoire size, and executive function. Coping flexibility was defined as reporting more strategies directed toward adjusting to, rather than changing, situations as they became uncontrollable. Older children without ADHD demonstrated greater coping flexibility than did younger children without ADHD or either age group with ADHD. The age difference in coping flexibility was mediated by older children's greater accuracy in perceiving decreases in controllability. Children with ADHD (both younger and older) reported more anti social strategies than did children without ADHD, a difference that was accounted for by their smaller repertoire of coping strategies. Programs directed toward enhancing coping flexibility may need to target different cognitive skills for children with and without ADHD. (Contains 1 table, 2 figures and 4 footnotes.)