We examine the fully nonlinear behavior of a thin liquid film in three spatial dimension for a large lateral extension. A partial differential equation is used for the spatiotemporal evolution of the height of the film. To take intermolecular forces in the liquid into account, we concentrate on a recently formulated model of Pismen and Pomeau, who derived an expression for the disjoining pressure only from the wetting properties of the fluid. Finally, the motion of a falling film on an inclined plane is studied within this model.