A polymeric composition consisting of water-soluble or water-swellable copolymers containing sulfo groups and nonionic polysaccharide derivatives, such as methylcellulose (MC), hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), methylhydroxyethylcellulose (MHEC), methylhydroxypropylcellulose (MHPC) and welan gum or diutan gum, and the use thereof as an additive in aqueous construction systems based on hydraulic binders, such as cement, lime, gypsum or anhydrite, is described. The composition can also be used in water-based paint and coating systems. The composition according to the invention exhibits a synergistic improvement of the properties and, when used in relatively small amounts, constitutes highly effective water retention agents in such construction and paint systems, which also achieve outstanding air pore stability and tack.