Thin polycrystalline films of PbSe incubated in SnCl 2 solution at 353 K were studied by X-ray diffraction and X-ray photoelectron spectroscopy with layer-by-layer etching Depth profiles of the film layers up to ~21 nm in thickness were obtained, and main chemical states of the elements at the surface were determined. The contact between the PbSe layer and tin (II) chloride aqueous solution was shown to result in tin introduction into the surface layers of the basic material, with its crystal structure perfection worsening at the same time.