For Environmental Impact Assessment procedures and appraisals, such as the Environmental Impact Assessment (EIA), the Strategic Environmental Assessment (SEA) or the Appropriate Assessment (AA) within the Fauna-Flora-Habitat regime, the examination of alternatives plays a crucial role. It has been an aim of the study to provide a well-structured description and clarification of the given ‘assessment of alternatives within the three instruments as well as of their practical application and implementation in various cases. Against the background of European legal acts, the accomplished literature research and the supplemented empirical investigation of the specific Austrian (administrative) practice, the application for the assessment of alternatives is of particular interest. In this context, the study specifies the respective practice-related criteria of such examinations, whereby individual cases of examples are analysed by both means of statistic and verbal-argumentative methods. Through the results of this study, it can be shown that in Austria it is of upmost importance to exactly differentiate and distinguish carefully when referring to the ‘assessments of alternatives with different procedural steps in the three instruments. While the SEA ensures a development of alternatives, and the EIA serves in particular a discussion on preferences of alternatives, the AA, conducted within the framework of the Natura-2000 regime, aims to establish an examination of proportionality through alternatives.