Liquidity play an important role on performance of firms listed in Stock Exchange. When there is a good flow of trading stocks, people could expect more financing through absorbing investors on market. The proposed study of this paper investigates the relationship between Tobin’s Q and illiquidity in some selected firms in Tehran Stock Exchange. The proposed study selects non-financial stocks over the period of 2001-2010. The result of the survey indicates that there is a negative relationship between illiquidity and Tobin’s Q but the ratio is approximately seven percent. In other words, as illiquidity increases by one percent, we could expect only a small change in firms’ performance.