The article features two kinds of constitutional proceedings - proceedings on complaints of citizens and requests from courts - that determine the uniqueness of representation of the interests of the client by the lawyer. The author analyzes the quality of uncertainty as the basis for proceedings in a case on the constitutional complaint in the Constitutional Court. Theoretical position on the inaccuracies of the language and other aspects of uncertainty are illustrated with the examples from the practice of the Constitutional Court of the Russian Federation. The author also determines which rights are to be protected by the Constitutional Court and how their violations can be expressed. The use of particular examples of judicial practice demonstrates the content of one of the constitutional rights - the right for qualified legal assistance, as well as the presence or absence of violation of this right. The subject of a constitutional complaint is determined. Consideration of the characteristics of the proceedings at the request of the court allows the author to conclude that in exercising representation on a civil or criminal case not only a judge but also a lawyer has the right to initiate a judicial inquiry in the Constitutional Court. The article analyzes the issues of representation in the constitutional (charter) courts of the subjects of the Russian Federation in the proceedings on citizens' complaints.