The hair treatment method includes applying to hair an effective amount of aqueous, alcoholic or aqueous-alcoholic hair treatment composition containing from 0.05 to 15 percent by weight of at least one as-yet-uncrosslinked hydrolytic precondensation product for forming an inorganic-organic hybrid polymer and optionally at least one film-forming hair-setting polymer, and subsequently crosslinking the as-yet-uncrosslinked hydrolytic precondensation product while the as-yet-uncrosslinked hydrolytic precondensation product remains on the hair to form the inorganic-organic hybrid polymer in order to provide long-lasting good hair setting. The hydrolytic precondensation product has an Si--O--Si network and is made by hydrolytically condensing at least one organosilane having crosslinkable groups with or without a network-modifying compound for modifying the crosslinking of the crosslinkable groups.