The present invention relates to a process for treating keratin fibres, especially the hair, comprising the following steps: —；application to the keratin fibres of a composition comprising one or more cationic acrylic copolymers comprising at least the units obtained from the following monomers: a) monomer derived from acrylic or methacrylic esters or amides and comprising at least one cationic group, and b) alkyl acrylate or methacrylate monomer, and—；application of heat to the keratin fibres using a heating tool, the application of heat possibly taking place before, during or after the application of the composition, preferably during or after.
