For many years, services attracted most of the foreign direct investment (FDI) in Central and Eastern European countries. Recently, a distinctive type of business services, i.e., advanced business services (ABS), has become the focal point in FDI in the region. This paper is aimed at defining the role of agglomeration economies in FDI in ABS in Poland. The topic is important from the policy point of view, as foreign investment is supported by the host country’s authorities, and various incentives are provided. The research method applied in this paper is the negative binomial regression. The outcome variable was the number of firms operating in ABS in particular regions. Explanatory variables pertain to the characteristics of 16 regions classified as Level 2 under the Nomenclature des Unités territoriales statistiques (Nomenclature of Territorial Units for Statistics or NUTS) in Poland. The main conclusion of the research is that agglomeration economies are important in the decision of the firms investing in ABS in Poland. The most important factor is the concentration of supply factors, such as abundance of educated employees. The specific features of ABS are associated with lower importance of demand factors in a region.