The present invention relates to a process for semi-permanent hair straightening and aftercare treatment and to a kit of compositions for use in this process. In the process of the present invention, the hair is firstly subjected to a straightening treatment using a straightening composition comprising at least one carboxylic acid of the formula (I): R—CO—COOH defined below and/or a hydrate thereof and/or a salt thereof. Then, a specific cleansing composition and/or a specific conditioning composition comprising at least one carboxylic acid of the formula (I): R—CO—COOH defined below and/or a hydrate thereof and/or a salt thereof are used as aftercare products in order to improve durability of the straightening effect.
