According to the definition in the Centers for Disease Prevention and Control (CDC), "Comorbidity means more than one disease or condition is present in the same person at the same time." So, essentially this means that anxiety disorder and ADHD may coexist in the same person. Still, the causes and symptoms are not necessarily the same.
To tell the difference between ADHD and anxiety, it is essential to be fully aware of the features of each of the disorders and then to find where they co-relate.