The structures of DNA-hexadecylamine and DNA-hexadecyltrimethylammonium bromide multilayer films obtained by two different approaches: layer-by-layer (LbL) adsorption and Langmuir-Blodgett (LB) technique were compared. Interlayer distance and DNA conformation in these films were determined by small-angle X-ray scattering, infrared and ultraviolet spectroscopy. The following results were obtained: (1) X-ray diffractrograms of the films indicated a distinct layer structure; (2) the interlayer distances for LbL films were less than for LB-films, made from the same components and (3) the double stranded DNA was included into the DNA-hexadecylamine film as a single-stranded formation, whereas DNA in the DNA-hexadecyltrimethylammonium film retained its double-stranded form. Structural models of LbL and LB films were created. (C) 2003 Elsevier Science B.V. All rights reserved.