Nanoparticles of lead iodide (PbI2) were prepared by exposure of Langmuir-Blodgett (LB) films of lead arachidate to hydrogen iodide. The photoluminescence (PL) spectrum of the nanoparticles consisted of three bands: an exciton band and two low-energy bands associated with stoichiometric and structural defects. The center of the exciton band was blue-shifted due to a quantum size effect. The PL spectra drastically changed when the temperature increased.