On belief-desire reasoning tasks, children first pass tasks involving true belief before those involving false belief, and tasks involving positive desire before those involving negative desire. The current study examined belief-desire reasoning in participants old enough to pass all such tasks. Eighty-three 6- to 11-year-olds and 20 adult participants completed simple, computer-based tests of belief-desire reasoning, which recorded response times as well as error rates. Both measures suggested that, like young children, older children and adults find it more difficult to reason about false belief and negative desires than true beliefs and positive desires. It is argued that this developmental continuity is most consistent with either executive competence or executive performance accounts of the development of belief-desire reasoning.