Hydropower generation and flood control are often presented as a classical case of conflicting objectives in water resources planning. Even though this is a well-known and accepted fact, very little has been done in the direction of quantification of these trade-offs in practical terms mainly considering multireservoir systems and different hydrologic scenarios. This article applies the Constraint Method to evaluate those trade-offs, taking as a case study the CESP (Sao Paulo Power Utility) multireservoir system of the Paranapanema River basin, located in southeast Brazil. This multiobjective analysis reveals what and how intense the trade-offs are between the conflicting objectives and serves as a guideline for CESP operational policy.