The usual methods of discipline, like reasoning and scolding, don't work with this child, because the child doesn't really choose to act in these ways. It's just that their self-control comes and goes. Out of sheer frustration, parents sometimes find themselves spanking, ridiculing, or screaming at the child, even though they know it's not appropriate. This leaves everyone more upset than before. Then they blame themselves for not being better parents.
Medication can help to control some of the behavior problems.
But more often, there are other aspects of the problem that medication can't touch. Even though ADHD primarily affects a person's behavior, having the disorder has broad emotional repercussions. For some children, being scolded is the only attention they ever get. They have few experiences that build their sense of worth and competence. If they're hyperactive, they're often told they're bad and punished for being disruptive.