Abstract: The invention refers to crystallization inhibitor compositions, which contain as the active component a copolymer of 4-vinyl pyridine and of acrylic acid esters, dispersed in an aqueous medium. They are suitable for use in paraffinic oils to prevent the deposition of solid paraffin on walls of containers and pipelines.While the known compositions which contain the same active component are not suitable for use under field conditions due to their high solidification temperature, the novel compositions can be used at temperatures as low as -15.degree. C. and the dispersions are quite stable on storage and have low viscosity.