There is a large body of literature that documents the relationship between the degree of ownership concentration and the firm's per-formance. The results are spread among many opinions. The purpose of this thesis was to determine whether there is any relationship between ownership concentration and firm performance in Romanian firms. I use a complex database, describing 356 firms listed on the Bucharest Stock Exchange RASDAQ market and I de-termine that there is a positive relationship between the largest blockholder and firm performance and even more this relationship is concave....