The invention relates to a method and system for determining a sharp panoramic image constructed from a group of projection images, especially the invention relates to defining a structure of the panoramic X-ray image of an area of a dentition and of jaws. The structure of a panoramic image to be generated from a group of projection images is determined by at least two crucial parameters, namely parameters of the central surface S of the sharp layer and thickness t(s) of the sharp layer, using penalty function F(S,t), which is at least a penalty function F3(S,t) of low-frequency changes in the computed panoramic image corresponding to the choices S and t(S). After computing F3(S,t) the best center surface and thickness function (in other words the sharpest layer of the panoramic image) is obtained by minimizing said penalty function F(S,t) over parameter space.