A medical tomography apparatus and method, a 3D dataset is generated in as picture elements arranged in a three-dimensional grid during the examination of a patient. Predefined surfaces are stored in a library and, dependent on the desired examination, one of the predefined surfaces can be selected with an input unit and thus the shape of an evaluation surface can be defined. Picture elements of the 3D dataset along the evaluation surface and used for constructing a two-dimensional image. A pre-defined surface is selected from the library and is employed for determining the shape of the evaluation surface. The method and the apparatus can be particularly employed in a simple way for the multi-planar reconstruction of a two-dimensional image along a multiply or arbitrarily curved surface.