Professional assessment system, which is a collection of well-thought and logically selected elements constitutes a key sub-system of human resources management system. Assessment systems together with changes in the organisation itself and its surroundings are subject to modifications, including they are subject to processes of improvement targeted on facilitation of implementation of the processes and increase of its effectiveness and suitability in relation to undertaken stuff-related activities. Bering in mind the functions of the assessment system, the purpose of this article is to indicate the changes which took place in professional assessment system of police officers over the past sixteen years, including improvement of critical analysis both of the actual shape of the system as well as its earlier versions. The article also contains suggestions of further changes in the system, the implementation of which would allow to supplement the recent system with aspects that remained so far unregulated as well as to lead to increase of objectivity of expressed professional opinions and uniformity in their preparation.