The category of “knowledgeable (experienced) persons” is not limited to experts only. Arbitration assessors and specialists are also referred to as knowledgeable persons; some scholars believe that a witness and even a judge can perform the functions of a knowledgeable person. The article focuses on the figure of a specialist, his consultations and responses to court inquiries. There is a lack of unification of the norms on the participation of a specialist in the Civil Procedure Code and the Arbitration Procedure Code of the Russian Federation. The effectiveness of seeking advice from a specialist is substantiated – this is a faster and less costly way of obtaining special knowledge necessary for considering a case. Consultation and examination are mutually complementary, the consultation may precede the examination, or, on the contrary, follow after the completion of the examination of the expert opinion, when questions have arisen to such a conclusion and the problem is solved with the appointment of additional or repeated examinations. The consultations are varied and subject to classification. It is substantiated, based on the differences in the nature of the consultations, that the consultation of a specialist on the use of technical means in the study of evidence cannot be compared with the consultation of a specialist on a complex scientific issue. As a classification criterion, the author proposes to consider the need for research and assessment of consultation, or the lack thereof. In the latter case, there is technical assistance and it would be legitimate not to classify it as evidence. However, research and assessment of the information presented is an attribute of working with evidence, therefore, in such cases, the status of evidence should be recognized for consultation.