The publication is devoted to analysis of the expert interviews materials conducted in 2017 by the author team of the public relations department in business of St. Petersburg State University. The research is supported by the Federal project “Professional practices, ethics and professionalism in contemporary Russian PR”. The subject matter of this article is existence of the unwritten rules in the professional community. The article provides views of experts on the presence or absence of these rules, as well as their place and functions in professional communication.