The regeneration of LB films of (trimethylsilyl)cellulose (TMSC) (1) to ultrathin films of cellulose (2) is monitored by X-ray photoelectron spectroscopy (XPS). Subsequent chemical derivatization of these regenerated cellulose films with trifluoroacetic anhydride (TFAA) (3) to give the corresponding cellulose trifluoroacetate (5) was proven and followed by XPS as a function of exposure time in order to study hydroxyl accessibility. The derivatization behavior of regenerated cellulose films is compared with literature data on bulk cellulose materials with varying degrees of crystallinity. In contrast to the latter, the functionalization kinetics of the regenerated cellulose films indicates a low hydroxyl accessibility in conjuction with a high degree of order in these films.