In this paper, the relationship between firm performance’s combinations and differences as well as the timeliness of actual and scheduled third-quarter report disclosures is examined by regressing on data extracted from the semi-annual and the third-quarter reports of Chinese listed companies between 2003 and 2004. After controlling for the possible impact of semi-annual report disclosures, stock exchanges, firm size, ratios of tradable A-shares and B-shares, and so on, the results indicate that managers of listed companies may have the incentive to manipulate information in the actual and scheduled third-quarter report disclosures; the rule of “releasing good news earlier than bad news” is thus not strictly complied with. This paper further indicates that a firm’s performance, its combinations and differences, have a significant impact on the timeliness of disclosures of these two reports. I therefore suggest minimising the probability of information manipulation of listed companies, boosting investor relation management to safeguard the rights of small and medium shareholders, and enhancing the timeliness of information disclosures of Chinese listed companies.