Applications of non-contact atomic force microscopy (NC-AFM) to the investigations of organic molecular films are described. Molecular arrangements in model organic films such as fullerene (C₆₀) thin films on a Si(111)-7×7 surface and self-assembled monolayers (SAMs) of alkanethiol molecules deposited on a Au(111) substrate were successfully imaged. Since both samples have been intensively studied by STM, they are suitable for the comprehensive understanding of the contrast mechanisms in NC-AFM. Some technical issues in NC-AFM imaging of molecules are also discussed. Furthermore, Kelvin probe force microscopy (KFM) was used to map the local surface potential of molecular films of oligothiophenes as well as fullerenes. Since surface potential of molecular films is caused by either polarization of the film originating from the dipole moment of molecules or the charge transfer at a molecule-substrate interface, the local potential variation is directly related to the electronic structures in the films on the substrate.