ADHD is a condition, which is presumed to be of neurological origin. The person with ADHD finds it difficult to inhibit (control) impulses, so he or she pays attention to everything in the environment. People who are gifted and talented also have the ability (in fact, the need) to pay attention to lots of things. That's what makes school so boring for so many kids who are very bright. What makes the two people different is the efficiency of the scanning or how well the person understands and organizes what he sees, hears, or touches. The person without ADHD takes in information, analyzes it, categorizes it, discards irrelevant data and integrates the new data with stored information in an instant. This is done in a very efficient (and by the way, satisfying) manner. Whether a person is a professional basketball player or an artist, he goes through this process over and over again in order to be successful. On the other hand, the person who is impulse-driven flits from stimulus to stimulus. He or she is much like a steel ball in a pinball machine -- sometimes reacting to a stimulus, sometimes performing an action on purpose, but most often acting in a random, unplanned fashion. And, the whole time going downhill, so to speak. Some parents of children with ADHD who are really physically fit fret over their child's frustrating lack of success in soccer -- because she runs the wrong way down the playing field!
You might notice that when some people with ADHD are motivated by something, they can be intensely focused (a video game, for example). In a gifted person, we might call this "sticktuitiveness." In the person with ADHD, this is often really what is called perseveration, or the inability to not pay attention or to shift easily from one thing to another. There's also a psychological component operating here, too. Why give up playing one game that you love to do something (like homework-ugh!) that you despise? On the on the other hand, artists and athletes (and other gifted people) stick with something for the purpose of mastery. They get things a little more right with each repetition. In children with ADHD, getting something right feels more a matter of chance. While practice and drill do result in gains, their learning curve is not smooth and upward like the basketball player practicing foul shots; it's more up and down -- and more frustrating. This is not to say that children and adults with ADHD cannot master things. The key to building a good self concept in children with ADHD is finding those things that he or she does well and using these rewarding feelings that come from these activities to balance the frustrations from other parts of their life.
So what about the person who is gifted and who has ADHD? The successes and the frustrations are both very intense, but may be erratic. The combination of being bright and impulsive means that you may act without thinking but you will probably be right more often than the other guy who is just impulsive. Unless a child understands his or her intellectual strengths and understands the potentially negative impacts of the ADHD, they may be confused by their inability to sustain success. Self-understanding (often aided by counseling) goes a long way in helping a person with this unique combination of traits and talents attain his or her fullest potential.