In this article, we present a comparative study of a developed new formal mathematical model of risk assessment (FoMRA) with expert methods of risk assessment in the information systems (IS). Proposed analysis verified the correctness of theoretical assumptions of developed model. In the paper, the examples of computations illustrating the application of FoMRA and known and accepted throughout the world methods of risk assessment: MEHARI and CRAMM were presented and related to a specific unit of the public administration operating in Poland.