Abstract. Aim. To propose a methodological approach to probabilistic forecasting and comparison of the performance of systems producing material and/or information products, to illustrate the practicality of the proposed approach with examples in various applications. Methods. Methods and models based on the methods of probability theory and system analysis, brought to implementation in national standards of system engineering, are proposed for use. Results. Models of complex systems producing material and/or information products are adapted for predicting and comparing for the same system under different operating conditions, for different systems applied to the same time period or for different time periods with the same or different duration and operating conditions. The proposed approach covers methods for assessing the relative part of the system functions performed with acceptable quality, estimating costs in the life cycle of systems, assessing the relative degree of satisfaction of stakeholders associated with quality and costs in system operation. Conclusions. The efficiency of the proposed methodological approach to probabilistic forecasting and comparison of the performance of systems of various applications under conditions of uncertainty is demonstrated. The approach can be used for system analysis and optimisation of the performance of systems producing material and/or information products, substantiation of quantitative system requirements and engineering solutions aimed at meeting the needs of stakeholders.