Does a child and adolescent psychatrist have more knowledge in adhd cases and additional training than a normal psychatrist ?

Child psychiatrist: General psychiatry requires 4 years' residency training after medical school. Child ; adolescent psychiatry requires 2 additional years beyond general psychiatry. However, many child and adolescent psychiatry programs training to begin during year 4 of general psychiatry -- so the the total required is 5 years. Both general ; c;a psychiatrists are trained to treat adhd, but c;a sees more of it.

Yes: 2 additional years in a University setting which is called a child fellowship. This is after completing the 4 year adult psychiatric training in residency.