Recently indications amount that Attention-Deficit Hyperactivity Disorder (ADHD) does not vanish during adolescence, but can continue to exist into adulthood. In this article, the literature concerning ADHD in adults (ADHD-A), particularly published in the past five years, is reviewed with regard to the validity and reliability of the diagnosis ADHD-A. Although further research is necessary, the results of this review provide provisional support to accept the diagnosis ADHD-A as sufficiently valid and reliable.