This paper investigates the effect of the firm life cycle on the inter-company accounting comparability. The firm life cycle theory suggests that firms, like living organisms, pass through a series of development stages. Each firm life cycle stage has important characteristics that economic environment, firm structure and management strategies of the firm vary significantly with the corresponding stages(Miller and Friesen, 1980; Quinn and Cameron, 1983). Accounting information reflected on financial statement is also different depending on life cycle. This study examines whether firm life cycle impacts on financial reporting comparability. Comparability of accounting information is a qualitative characteristic that enables users of financial statements to identify similarities in and differences between two sets of economic phenomena (definition in K-IFRS). Comparability lowers the cost of acquiring firms and processing information, which increases the overall quantity and quality of information available to investors. Prior studies show that high comparability also improves analyst forecast accuracy (De Franco et al., 2011; Kang et al., 2013) and the ability of current stock return to reflect future earnings(Choi et al., 2014). The research on the determinants of comparability has investigated the role of accounting standards such as the adoption of IFRS, degree of enforcement ability(Yip and Young, 2012; Barth et al., 2012; Francis et al., 2014). Yip and Young(2012) show mandatory IFRS adoption improves comparability in 17 European countries. Barth et al.(2012) investigate the comparability of non-U.S firms that adopt IFRS with that of U.S firms. They found that non-U. S firms adopting IFRS have greater comparability and comparability is greater for IFRS firms that adopted IFRS mandatorily, for IFRS firms domicied in countries with common law, for IFRS firms with high enforcement. Also, the role of auditors affects inter-company comparability(Francis et al., 2014). Each Big 4 audit firm has its own unique auditing process for interpreting and applying accounting standard(Francis et al., 2014). Because of this, two companies audited by the same Big4 auditor have more comparable earnings than two firms audited by two different Big 4 auditors. We expect firm life cycle affects accounting comparability based on following two explanations. First, earnings attributes vary across life cycle stage. Previous studies show main variable, earnings attributes, value-relevance vary across the life cycle. Second, the degree of matching and earnings management vary across life cycle stage. Based on the above discussion, we derive following two research hypotheses. First, two companies included in same life cycle have more comparable earnings than two firms included in different life cycle. Second, if a pair of firms has different(same) life cycle and one of the firms changes life cycle to have same(different) cycle, then they have more(less) comparable earnings after the change. We measure comparability in two ways. The first approach is to examine differences in accruals between pairs of firms in the same year-industry((Francis et al., 2014). The second approach is to examine differences in expected earnings between pairs of firms in the same year-industry given same economic events(De Franco et al., 2011). As for the firm life cycle, we adopt a composite measure based on the three growth rates for sales, fixed assets, and the number of employees. We classify the sample into three stages: growth, mature and decline stages. To test the hypotheses, we use the 13,302 firm-pairs listed on the Korea Stock Exchange for the period of 2005 to 2012. The empirical results of this study are as follows. First, two companies included in same life cycle have more comparable earnings than two firms included in different life cycle. Second, if a pair of firms has different(same) life cycle and one of the firms change life cycle to have same (different) cycle, then after the change they have more(less) comparable earnings. This is the first study to investigate whether firm life cycle affects inter company comparability. This paper also provides evidence that firm life cycle is an important factor affecting accounting comparability.