The purpose of this research is to investigate the role of auditor type on comparability of profit and loss items in firms listed in Tehran Stock Exchange. To this end, 179 firms listed in Tehran Stock Exchange were selected during 2008 to 2014 years. After classifying, the numbers of 8610 firm-pairs were selected as research sample. To test the hypothesis, panel data were used. The results showed that audit firms’ clients of Association of Certified Public Accountants have more comparability than the clients of auditing Organization in the operating profit, net profit and total accruals structure. Also, clients of similar audit firms have more comparability than clients of two different audit firms in the profit structure. Clients of audit firm with a rating of "A" and "B" have more comparability than clients of audit firm with a rating of "C" and "D" in the profit and total accrual structure.