The ongoing 2D vs. 3D research debate from information visualization also affects software visualization. There are many 2D, 3D, and combinations of 2D and 3D visualizations for software representing its structure, behavior, or evolution. This study contributes findings to this debate and presents the results of analyzing the applications of 3D in software visualization with the objectives to outline the state-of-the-art, to reveal trends, and to identify research gaps. The analysis combined a systematic mapping study to get an overview and a systematic literature review to gain deeper insights. The relevant papers were identified by three different search strategies (manual browsing, keyword, and backward search). Starting with a set of 4386 publications from the fields of information and software visualization 155 relevant papers dealing with 2D & 3D or 3D software visualizations were identified. These papers were analyzed according to dimensionality, aspect, year, evaluation method, and application of the third dimension. In a nutshell, the majority of 3D software visualizations represents the structural aspect, is either evaluated using case studies showing working examples or not evaluated at all, and applies a 2D layout using the third dimension for displaying software metrics. In IVAPP'15: Proceedings of the 6th International Conference on Visualization Theory and Applications, 2015.