Building a competitive region is a long-lasting and highly complex process. The achieved level of competitive advantage is significantly determined by a precise diagnosis of the region's initial state and by the adopted direction of changes. This publication aims to demonstrate that application of the strategic reflection method (or, more precisely, of its third stage) allows to effectively realize such a diagnosis. By using it, it is possible to obtain the picture of the region's current level of competitive advantage (as well as its prognosis), not only in the absolute categories, but also in the relative categories describing the varied value of the region for different groups wanting to use it. Besides the methodology of proceeding, a practical example is provided to demonstrate the technical aspects of the method's application, and, through the interpretation of obtained results, their value for the assessment of the region's competitive advantage.