The transformations in nanosized lead films were studied by optical spectroscopy, microscopy, and gravimetry at different film thicknesses (d = 2-115 nm) and thermal treatment temperatures (T = 373-573 K). The kinetic curves of conversion were adequately described in terms of the linear, inverse logarithmic, parabolic, and logarithmic laws. The contact potential difference was measured for Pb and PbO films and photo EMF was measured for Pb-PbO systems. The energy band diagram was constructed for Pb-PbO sys tems. A model of the thermal transformation of Pb films was suggested, which included the stages of oxygen adsorption, charge carrier distribution in the contact field of Pb-PbO, and formation of lead(II) oxide.