In this paper we consider the uniqueness issues in Discrete Tomography. A special class of geometric objects, widely considered in the literature, is represented by additive sets. These sets are uniquely determined by their X-rays, and they are also reconstructible in polynomial time by use of linear programming. Recently, additivity has been extended to J-additivity to provide a more general treatment of known concepts and results. A further generalization of additivity, called bounded additivity is obtained by restricting to sets contained in a given orthogonal box. In this work, we investigate these two generalizations from a geometrical point of view and analyze the interplay between them.