The research topic focuses on the investigation of diagrams and architectural models as analytical and compositional architectural tools. During the first stages the concept of the diagram is analyzed by documenting the definitions and interpretations that have been attributed during the evolution of the architectural theory since the 20th century. Meanwhile, certain influential diagram theories are cited. At this point, not only the role of diagrams as a compositional tool is emphasised, but also the risk of using unsuitable compositional tools. In this thesis, it is crucial that any problems regarding the architectural diagram research are identified and further researched. In order to gain a better understanding of those concepts, the work of many influential architects that have contributed to the research and evolution of architectural diagram theory is reviewed and all different insights are taken into consideration. The review of certain intertemporal exercises involving diagrams and architectural models used in architectural courses all over the world can be considered as examples applied in architectural composition. Respectively, the result and the methodology analysis lead to the application of such exercises and their adjustment to contemporary technology (digital means). Finally, through the analysis of a project, the role and importance of diagrams and architectural models stands out as a crucial component of the composition process, from the preliminary stages until the completion.