Aqueous dispersions comprising a mixture of: A) from 0.05% by weight to 10% by weight of salts of perfluoropolyether di-carboxylic derivatives having formula: T-O--R.sub.f-T (IA) wherein T=--CF.sub.2--COOZ or --CF.sub.2CF.sub.2--COOZ wherein Z=Na, K, NH.sub.4, R.sub.1(R.sub.2)(R.sub.3)N wherein R.sub.1=R.sub.2=alkyl or hydroxyalkyl, R.sub.3=H, alkyl or hydroxyalkyl, R.sub.f is a (per)fluoropolyoxyalkylene chain having number average molecular weight between 500 and 10,000. B) from 0.01% to 5% by weight of water-dispersible or water-soluble cationic polymers, having a charge density, defined as number of equivalents per weight unit of dry polymer, higher than 1 meq/g of dry polymer.