The diagnosis of ADD/ADHD normally comes after age 6, or after formal schooling has begun. This occurs for a number of reasons: The diagnostic criteria for ADD/ADHD indicate that behaviors/symptoms must be present in at least two environments. Young children are often excitable and can become agitated when routines are disrupted. Overly active children do not necessarily have ADD/ADHD. The controversy surrounding ADD/ADHD can contribute to parents not seeking treatment or diagnosis as well as the reluctance of doctors to diagnose at such a young age. Children reach milestones at different ages making it difficult to measure development delays. The terrible twos can greatly resemble ADHD. Some children, however, have been diagnosed with ADD/ADHD as early as 2 years of age. Many parents of children diagnosed later have indicated that they knew something was different since infancy. Many parents, especially those with other children without ADD/ADHD have noticed differences in behavior and have documented ADD symptoms long before a child enters school.