Firms applying IAS and domestic standards could exhibit differences in accounting quality in the post adoption period because they differ in die period before the firms applying IAS adopt IAS, that is, the pre adoption period. To determine whether this is the case, we compare accounting quality of the two groups of firms in the pre adoption period. We find that differ-ences in our accounting quality metrics in the pre adoption period do not explain the differences in the post adoption period. In die pre adoption period, all but one of the quality metrics for firms that later apply IAS differ insignificantly from those for firms that do not apply IAS. The matched sample design might not fully control for differences in the economic environment. Thus, we also compare accounting quality metrics for firms applying IAS in the pre- and post adoption periods, thereby effectively using each firm as its own control for these differences. We find that firms apply-ing IAS exhibit higher accounting quality in the post adoption period than they do in the pre adoption period, with four of the eight differences being significant. Because the economic environment can change over time, we also test whether the increase in accounting quality for firms that apply IAS is greater than that for firms that do not. We find that, generally, the increase in accounting quality is greater for firms applying IAS, although almost, all of the differences in changes in accounting quality metrics are not significant.