In experiment Maxwell's displacement current (MDC) flows through the structure containing a metal electrode, an air gap insulating layer and the Langmuir monolayer on a water surface. MDC experimental results obtained during a lateral compression of the monolayer are analysed by a model based on the analogy with a non-ideal gas of polar molecules, assuming the Boltzmann statistics of orientational distribution. The theoretical model is presented for a monolayer of thin rodlike molecules (stearic acid) as well as for non-ideal thick amphiphilic units of substituted oligo(3-alkylthiophenes) and compared with experimental data. (C) 2004 Published by Elsevier B.V.