Liquid phase deposition polymerization (LPDP) is a recently reported method suitable for preparation of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT), with some similarities to vapor phase polymerization except the polymer film growth at the gas-solid boundary is replaced with growth at the liquid-solid interfacial layer. Film growth process by LPDP method is largely unexplored compared to vapor phase polymerization and it is essential to understand the film formation process in order to use the full potential that this new method entails in preparation of highly conductive PEDOT films. In this study, in situ measurements of electrical resistance and transmittance were used to monitor these key parameters of the polymerizing films during LPDP, revealing a three-stage polymerization process. Films with conductivity of 362 S/cm were prepared and the detailed information from in situ measurements opens up research directions to further improve the properties of the PEDOT films. Cyclic voltammetry was used for investigating the electrochemical behavior of the PEDOT films.