The article presents a method for determining and ranking significance of the criteria of an information system for managing projects and programs (hereinafter, PMIS) based on the concept of subjective probability with the help of expert assessments. The method of expert assessments is implemented by processing the opinions of experienced specialists on the possible values of losses and (or) the probability of their occurrence. It is also used in non-formalizable problem situations, when the lack of a sufficient array of information or its unreliability does not allow the use of purely formal mathematical methods. When analyzing the PMIS choice, expert assessments can be used, firstly, to form a subjective assessment of one or another PMIS with the subsequent use of this information in order to quantify it using statistical methods. Secondly, for a qualitative assessment of the PMIS choice in terms of determining their rank significance, priority in an ordered list of PMIS criteria. As the main stages of the proposed methodology, the following are proposed: 1) development of a list of assessed PMIS criteria and formation of a list of experts; 2) conducting a survey of experts in order to obtain a set of individual expert assessments according to the PMIS criteria; 3) calculation of the average assessment criteria of the PMIS; 4) checking the consistency of expert opinions on the rank significance of the assessed PMIS criteria based on the Kendall coefficient of concordance; 5) summing up the results of expert assessment of the PMIS criteria. The practical aspects of the expert assessment are considered: calculation tables, the method of filling them, processing and analyzing the results. The method of expert assessment of the PMIS criteria was further developed, thanks to which a set of effective and functional criteria was determined, which will be taken into account when developing technical requirements for this system