The Langmuir-Blodgett films of N-octadecyl-8-hydroxy-2-quinoline carboxamide (HOQ) deposited from subphase containing metal ions were investigated by X-ray photoelectron spectroscopy (XPS). The amphiphilic HOQ with its complexing head group in contact with the aqueous phase can form metal complexes with the metal ions present in the aqueous phase. The formation of HOQ-metal complexes leads to the appearance of new XPS peaks assigned to the metal ions. The information on stoichiometry provided by XPS indicates that a metal ion is coordinated by one HOQ molecule for transition metal ions of the fourth period, but by two HOQ molecules for the metal ions after the fourth period.