The invention relates to a method for preparing 5-hydroxymethylfurfural (HMF) by reacting hexose in water and in the presence of carboxylic acid. The present invention further relates to the preparation of 5-hydroxymethylfurfural (HMF) by reacting hexose in water and in the presence of carboxylic acid and of a heterogenous acid catalyst. The invention also relates to an HMF-rich carboxylic acid solution.