This paper deals with duties of investment bankers except broker-dealers, which include investment advisors, fund managers and trustees (hereinafter investment advisors) under the Financial Investment Services and Capital Markets Act in Korea (hereinafter the Act). Traditionally, broker-dealers have been always subject to the duty of care and sometimes a fiduciary duty. Thus, the most important issue regarding their duty is when they are subject to either the duty of care or the fiduciary duty. In a latter case, they should prove that they did their best to pursue the benefit of clients and otherwise they should compensate damages which are based on a simple calculation method provided by the law. In contrast to broker-dealers, investment advisors are always subject to the fiduciary duty in principle. Thus, it is a very rare case where investment advisors are not liable under safe harbor provisions beyond the fiduciary duty. The main reason why they are more liable than broker-dealers is that they have a firsthand duty to protect the interest of clients as fiduciaries and should not stand on a conflicting and contrary position in order to enhance their own interest. The Act proclaims the duty of care and the fiduciary duty against investment advisors, fund managers and trustees separately. Thus, a relationship between the duty of care and the fiduciary duty should be clarified. Some one may argue both duties are so different that all the business of conduct regulations, including regulations prohibiting conflicting interests, should be clearly divided into two parts under both duties. This paper argues that both duties are fundamentally same in terms of investment advisors, so that division works above based on a different view of both duties are meaningless. Traditional arguments regarding inter-relationships between both duties are also unnecessary in these investment advisor sectors. The concept of the fiduciary duty either under the Corporation Act or the Act is quite different since the former has treated the fiduciary duty as a kind of the duty of care but the latter has acknowledged the fiduciary duty as a more weighted one than the traditional duty of care. Nevertheless, nobody understands a reason why the Corporation Act and the Act are using the same word. Key rules such as the best interest rule and the best execution rule should be adopted since these rules are fundamental and significant in the fiduciary duty context. Strict rules severely limiting rights and imposing duties should be provided by the Act in essence especially under the rule of law and the due process philosophies. Soft dollar related provisions are not exceptions to these philosophies. All these arguments are modeled on the U.S. Investment Advisors Act of 1940.