It is proposed a method of treating a subterranean formation including providing a suspension of colloidal particles prior to the injection of a treating fluid based on an aqueous fluid comprising a thickening amount of a viscoelastic surfactant. The colloidal particles help to reduce fluid losses into the formation. According to a second embodiment, the treating fluid includes a hydrophobically-modified polymer, said hydrophobically-modified polymer being present at a concentration between approximately its overlap concentration c* and approximately its entanglement concentration ce. The method is particularly useful for fracturing operation in medium to high permeability formation.