IFRS 8 and its counterpart HKFRS 8 supersedes IAS 14 and HKAS 14 in 2006 to upgrade segment information disclosure that is increasingly becoming important financial information in investment decision making. There is little understanding of the changes in the quality of firms’ segment disclosure as a consequence of implementing the new standard in Hong Kong’s unique political and economic environment. This study attempts to document the usefulness of segment information disclosure by Hong Kong listed firms as a consequence of implementing HKIFRS 8. The study employs the value relevance of accounting information theory as a measure of usefulness of segment disclosure where segmental data are analysed by the portfolio return approach and regression analysis. The purposive sampling method is used to obtain samples from Hong Kong listed firms. The study results indicate that implementation of HKIFRS 8 has improved the usefulness of segment information disclosed by Hong Kong listed firms.