ABSTRACT In recent years, firms tend to hold conference calls to have more communication with market investors so that to promote information transparency and to reduce the information asymmetry between insiders and outsiders. By holding conference calls, the communication and interaction between management and investors can be more direct and the disclosure of information. The primary objective of this paper is to study the effect of conference calls, self information disclosure, to firm and investors. This study examines the association among conference calls, product diversification on performance. Using a sample of publicly traded firms listed on the Taiwan Stock Exchange from 2008 to 2013, we find that to hold and number of conference calls would positively moderate effect on the relationship of product diversification on performance. The results also show that the frequency of conference calls becomes higher, the performance of product diversification becomes higher.