Background: An estimated 4.4 million children in the United States suffer from Attention Deficit/Hyperactivity Disorder (ADHD), and most would benefit from a low-cost, side-effect-free way of managing their symptoms. Previous research suggests that after isolated exposures to greenspace, children's ADHD symptoms are reduced. This study examined whether routine exposures to greenspace, experienced through children's everyday play settings, might yield ongoing reductions in ADHD symptoms. Methods: Data on 421 children's ADHD symptoms and usual play settings were collected using a national Internet-based survey of parents. Results: Findings suggest that everyday play settings make a difference in overall symptom severity in children with ADHD. Specifically, children with ADHD who play regularly in green play settings have milder symptoms than children who play in built outdoor and indoor settings. This is true for all income groups and for both boys and girls. Interestingly, for hyperactive children, the apparent advantage of green spaces is true only for relatively open green settings. Conclusions: These and previous findings collectively suggest that it is time for randomised clinical trials testing the impacts of regular exposure to greenspace as a treatment for ADHD.