Too often consultation is dominated by the attitudes of professionals and their "adult-oriented" decision-making systems, it argues.
Young people, especially those with disabilities, have little experience of such a system and lack confidence in expressing their views.
"Some . . . may find certain issues difficult to talk about and it is vital that they are not put under pressure to do so. All children and young people involved in consultation should be aware that they can stop participating at any point," the advocacy agency states in a special publication on accessibility strategies.
It advises that many of the more difficult to reach often do not have their views sought or listened to.
Children in Scotland itself consulted with Capability Scotland, George Watson's College, Harmeny School, Leith Academy and Uddingston Grammar before publishing Consulting with children and young people on accessibility strategies: a good practice guide.