In February, an independent counsel cleared Lee of financial fraud allegations that he colluded with Kim in a 2001 stock price manipulation case.
Kim was accused of making millions of dollars by rigging stock prices from a separate investment company and fleeing to the US with the ill-gotten gains.
Lee's liberal rivals had alleged that the money used for the stock manipulation came from a third investment firm, known as BBK, and that Lee was its real owner.
Lee has strongly denied the allegations, calling them a plot by political rivals to discredit him.
Lee, who is on a visit to the US, has meanwhile been drumming up business interest in his country.
Senior executives at Wall Street banks said on Wednesday that Lee's free-market policies would rekindle appetite for investing in Asia's fourth-largest economy, which has been seen as unfriendly to foreign investment in recent years.
"Lee has a very inviting approach. I think financial firms' investment to Korea will certainly rise under his leadership," Robert Hormats, vice-chairman of Goldman Sachs International told Reuters.
Western firms had become increasingly concerned about investing in South Korea, amid a public backlash against foreign investors, such as Newbridge Capital, after they made handsome returns buying up distressed assets in the wake of the 1997-98 Asian financial crisis and reselling them years later.
This could change under Lee, an outspoken advocate of open-market policy, Wall Street chief executives said.
"Lee sounded quite inviting and forward-looking. I think the new president sent some very encouraging signals," said Robert Shafir, chief executive of Credit Suisse America.
Addressing an investor forum on Wednesday, Lee reaffirmed his pledge to entice foreign investment by removing regulations and making costs for labour and factory sites affordable.
"Excessive regulations are always the biggest barrier to business activities of both foreign and domestic companies," Lee said.
"All rules and regulations that do not conform to the global standards will be revised."