After the separation of management from ownership, and the emergence of the agency theory, the board of directors has been identified as the mechanism of internal control and governing means in firms. Hence, this study, attempting to provide a new approach to the importance, quality and quantity of the board of directors, investigates the impact of operations of a firm on the structure of board of directors. In this study, the sample consists of 60 firms listed in the Tehran Stock Exchange (TSE) from 2000 to 2009. The statistical method of analysis utilizes the Logistic regression model and ordinary least squares regression model with panel data. The findings revealed that the scope of operation measures, namely firm size, firm age and debt ratios, didn’t significantly affect the structure measures of board of directors, including size of the board, percentage of outsiders in the board, appearance of one of the outsiders as the chairman of the board, and the presence of at least three outsiders in the board. However, the ownership percentage of institutional shareholders had significant and negative effect on the structure of board of directors. Also, type of industry didn’t have significant impact on the structure of board of directors in the studied firms.