A new approach for the analysis of X-ray diffraction patterns to obtain the structure of Langmuir-Blodgett (LB) films is reported. In particular, to solve the "phase problem" we apply a direct method, essentially a pattern recognition approach, which was recently proposed to determine without assumptions the structure of liquid-crystalline phases, This approach is used to analyse two different types of samples, namely LB films of fatty acid salts and of bipolar lipids extracted from thermoacidophilic archaeon Sulfolobus solfataricus. As a result, the electron density profiles allow us to fully characterize the molecular arrangement in both the investigated films.