There is a common agreement in the scientific community that communicating uncertain hydrometeorological forecasts to water managers, civil protection authorities and other stakeholders is far from being a resolved issue. This paper focuses on the communication of uncertain hydrological forecasts to decision-makers such as operational hydrologists and water managers in charge of flood warning and scenario-based reservoir operation. Results from case studies conducted together with flood forecasting experts in Europe and operational forecasters from the hydroelectric sector in France are presented. They illustrate some key issues on dealing with probabilistic hydro-meteorological forecasts and communicating uncertainty in operational flood forecasting.