Objective: Numerous factors, including genetic, neurobiological, neurochemical, and psychological factors, are thought to be involved in the development of anxiety disorders. The latest findings show that the pathophysiology of anxiety disorders might be associated with oxidative stress and lipid peroxidation; however, no studies have so far investigated lipid peroxidation markers in children with anxiety disorders. Serum levels of lipid hydroperoxide (LOOH) are a reliable marker of lipid peroxidation. Paraoxonase and arylesterase are two enzymes that protect against such peroxidation, and might also be diagnostic markers. In this study, we investigated whether there are associations between anxiety disorders and lipid peroxidation markers in children, and assessed the diagnostic performance of these markers.