In this Master Thesis an Enterprise Architecture Decision Making analysis is proposed within the field of Enterprise Architecture. A case study at a company within the financial sector has been conducted for validation of the proposed analysis. Firstly, the Enterprise Architecture Analysis Tool (EAAT), which has been developed by the Industrial Information and Control Systems (ICS) department of KTH, is described. This tool has been used during the whole Case Study in order to create present and possible future state models for measuring Service Availability. These models, which are based on a Metamodel, make possible the analysis of the Service Availability. Finally, some future research suggestions in the context of decision-making in Enterprise Architecture with EAAT are given.