Langmuir-Blodgett films of two mixed cadmium fatty acid salts were deposited and investigated by small-angle X-ray scattering. For one of the systems investigated (a mixture of stearic and behenic acids) it was found that for a 1:1 ratio, the lattice spacing corresponds to the sum of stearic and behenic acid salts, while, for any other ratio, the X-ray patterns contained two systems of reflections, each of them corresponding to one of the pure acid salts (49.0 angstrom and 58.5 angstrom, respectively). The other system investigated (a mixture of behenic and palmitic acid salts) gave a completely different result: a single phase was present for any molar ratio of compounds and the lattice spacing varied with the molar ratio itself.