The effect of thermal annealing in air at 350 °C on the photoconductive behaviour of chemically deposited PbSe thin films is investigated. A model of small crystallites embedded in an amorphous PbSe matrix is proposed for the discussion of the sharp drop in resistance in the first minutes of heating and for the shift in photoconduction maximum. The developing of photoconductive and resistance maximums due to thermal annealing is evidenced.