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Power systems around the world are changing due to the rapid transformation of the generation mix. Unprecedented configurations of the power system may increase the exposure to failures, and thus, lower security of supply. At the same time, the secure development of the system cannot neglect cost considerations. This demands for adequate tools to assess and prepare for future scenarios of the energy transition. In this paper, a risk-informed approach for generation and transmission expansion planning is developed. The approach integrates cost-based generation and transmission expansion planning and risk-based transmission expansion planning. Interfacing these two models to perform coordinated generation and transmission expansion planning results in solutions that are cost-effective, account for the risk implications of the systemic changes, and guarantee system security. The risk-informed coordinated generation and transmission system expansion planning is performed for the Swiss power system which is modeled in full detail for the year 2050. To account for electricity exports and imports, the four surrounding countries are considered in an aggregated manner and their 2050 capacities are projected assuming a net-zero scenario. The results of the risk-informed coordinated expansion planning show that the pure cost-minimization approach applied to either generation or combined generation and transmission expansion planning does not necessarily lead to a reliable power supply in Switzerland. In fact, not accounting for reliability leads to expansion solutions that may incur up to 16 times higher demand not served compared to the reference year 2018. This highlights the importance of considering in-depth system security analyses in power system expansion planning., Energy, 280, ISSN:0360-5442, ISSN:1873-6785