Microphase separation and morphology of thin films of ABC triblock terpolymers are studied with a self-consistent-field theory. Thin films of poly(styrene)-block-poly(2-vinylpyridine)-block-poly(tertbutyl methacrylate) (SVT) triblock terpolymers are modeled as A(3)B(4)C(12) Gaussian chains confined in a slit. The bulk morphologies are found to be much more robust with respect to the interaction parameters when compared to the morphologies in the confined situation. By adjusting the interaction parameters between the polymer components and the surfaces, we can model the experimentally observed sequence of surface structures as a function of the film thickness. At well-defined film thicknesses a highly ordered perforated lamella structure is observed. We systematically explore the influence of film thickness, surface field, and the interaction parameters between the different polymer components on the phase behavior.