Realization of synergy between related business units, such as a foreign subsidiary and the corporate core business, is crucial to successful implementation of a competitive international strategy. Exploitation of relatedness facilitates the sharing of knowledge relevant to competitive advantage across the corporation. This chapter explores the role of managerial cognition and biases that may appear when managers specify relatedness among business units. Understanding the impact of such obstacles facilitates realization of the synergy potential of relatedness. Without sharing resources, each business unit would work separately, resulting in risks for sub-optimization and a difficulty to achieve competitive advantage by means of extending corporate efficiency. The extent of cost-reduction, or increase of revenues, manifests synergy realization. This chapter contributes to the understanding of managerial cognition in the context of implementation of competitive international strategy. The chapter shows that biases arise when individual managers judge similarities, and the biases are linked to the specification of relatedness in terms of the choice of business units to compare and the choice of relatedness dimensions. Furthermore, for both choices, conflicting views of managers may appear that may cause cognitive dissonance.