The relation of the managerial efficiency and leadership styles are analysed in this paper. We conducted an empirical study in a Iranian power supply company (HEP). The dominant leadership style in HEP is consultational, which the organization, according to postulates of this research, brings closer to the top global companies, considering that the tendencies in leadership styles point to the ... [Show full abstract] need for a new generation of leaders which will be essentially different from the traditional manager. We have determined that there is a significant interdependence between leadership styles of HEP’s managers (measured using Likert’s method) and the degree of management work efficiency (measured using the adjusted Mott’s technique); the closer the leadership style is to System 4, that is participational, the higher the managerial efficiency is. Also, we have found that there is no significant difference between lower and middle management in HEP, concerning the relation between leadership styles and efficiency. This means that both levels get better grades for its efficiency if they belong to a consultational and participational leadership style.