The paper regards the possibility of using fine-grained power industry wastes (fly ashes) or coal mining wastes (post-flotation sludges) for flood embankments sealing. Owing to the fact, that those are hydraulic embankments, and they are subjected periodically to the influence of water, they should meet requirements prescribed to this type of structures, referring mainly to the stability and leak tightness. An analysis of granulation, water permeability and compactibility of chosen fly ashes and coal mining sludges in the aspect of their applying as sealing screens in flood embankments was carried out in the paper. It was stated that using fly ashes or coal mining sludges for sealing the embankments is efficacious, since it contributes to getting the value of permeability coefficient in the order of 10-7–10-8 m·s-1, that is less than the required one (k < 10-6 m·s-1) for the materials used for hydraulic embankments. ...