The main aim of this study was to examine the moderating effects of attention deficit hyperactivity disorder (ADHD) on anxiety disorders in children. Data were analyzed from a large referred sample of children with anxiety disorder without comorbid ADHD (anxiety disorder, N = 253), anxiety disorder plus comorbid ADHD (anxiety disorder + ADHD, N = 704), and ADHD without comorbid anxiety disorder (ADHD, N = 511). Children were comprehensively assessed, including by structured diagnostic interview (K-SADS-E). Overall rates of individual anxiety disorders, as well as age of onset and severity of illness were not significantly different in the presence of comorbid ADHD. School functioning in children with anxiety disorders was negatively impacted by the presence of comorbid ADHD. Frequency of mental health treatment in children with anxiety disorders was significantly increased in the presence of comorbid ADHD. ADHD had a limited impact on the manifestation of anxiety disorder in children suggesting that ADHD and anxiety disorders are independently expressed.