The basic purpose of this study is to examine the association of ownership structure (OS) with the value of business firms (VBF). By using panel data techniques, the relationship between OS and VBF has been statistically tested. OS is used as an explanatory variable, whereas, for measuring VBF, accounting base performance measures (short term performance) include return on assets (ROA) and return on equity (ROE) and market base performance (long term performance) has been measured through Tobin's Q. The study also emphasizes the firm age as an interactive variable. Ownership role is examined from the perspective of agency theory (AT) and by using resource dependence theory (RDT). The sample consists of 135 companies and having 1890 observations of the non-financial sector listed on the Pakistan Stock Exchange (PSX) for the time period 2004 to 2017. Researchers have applied descriptive and inferential statistical techniques to analyze the gathered data. Findings reveal that some dimensions of OS significantly influence the short term and long-run firm performance (FP) under the interactive role of age. The study aims at contributing useful knowledge generally for the financial community, and specifically for investors, researchers, and regulators.