A process for preparing aqueous solutions of homo- or copolymers of acrylic acid by means of free-radical polymerization of acrylic acid and optionally water-soluble, monoethylenically unsaturated comonomers in an aqueous medium in the presence of at least one water-soluble initiator and of at least one water-soluble regulator, wherein the polymerization is conducted by means of a continuous process, and wherein, after the polymerization, low molecular weight components are at least partly removed from the resulting aqueous polymer solution. For the polymerization, preference is given to using microstructured mixers and reactors. Preference is given to using at least one reactor and/or mixer with microstructures for the process.