The author discusses the most important procedural issues concerning a complaint about lengthiness of a proceeding, including the composition of the bench in the complaint case, adequate use of regulations regarding a complaint proceeding which are in force in the proceeding being complained about (civil, penal, court and administrative one) as well as the court ruling in the subject-matter of the complaint. Referring to the doctrine opinion and judicial decisions, the author concentrates on a complaint about the lengthiness lodged in the course of the penal proceeding. The article is based on the state of law after 1 May, 2009, although the comparative comments refer to the state of law binding before that date.