An ultrathin film of poly(N-neopentylmethacrylamide) (PnPMA) prepared by the Langmuir-Blodgett technique was examined as a high-resolution self-developed photoresist. The properties of the LB films were investigated using W absorption spectra and X-ray diffraction. Fine lines and spaces with positive-tone patterns on the LB film were achieved solely by deep W irradiation (self-development). A fine gold pattern with a resolution of 1.5 mum was obtained by etching patterned LB film on gold film deposited on a glass substrate, indicating that 20 layers of LB film (about 20 nm) is stable against wet etching.