A look at the key issues in the South Korean elections:
Front runner Moon Jae In of the Democratic Party has had to harden his position on North Korea to counter criticism that he is too soft on Pyongyang. He had earlier said he would push for the restarting of the six-party talks on ending the North's nuclear programme, and work towards a peace treaty with the North.
But on Thursday, he warned that Pyongyang would face deeper isolation and a prolonged freeze in ties with Seoul if it carries out another nuclear test.
Mr Moon's spokesman yesterday said the deployment of the Terminal High Altitude Area Defence (THAAD) should be "immediately suspended" ahead of a decision by the next government.
His closest rival, Mr Ahn Cheol Soo of the People's Party, has unequivocally called for the deployment of THAAD and accused China of not doing enough to halt North Korea's missile and nuclear programmes.
ECONOMY AND CHAEBOL REFORMS
The ouster of Park Geun Hye as president on March 10, following months of mass demonstrations, once again exposed the cosy ties between politicians and big business.
Mr Moon, a former human rights lawyer, has promised to end the practice of pardoning convicted corporate criminals and to break up the nexus between big business and the government in Asia's fourth- largest economy.
Mr Ahn proposes strengthening the Korea Fair Trade Commission to ensure tighter oversight of chaebol monopolies and oligopolies.
The two candidates offer broadly similar economic policies. The biggest difference is that Mr Moon advocates government action, such as increasing public sector employment, while Mr Ahn, a former software entrepreneur, calls for the private sector to take the lead.
SOURCES: NIKKEI ASIAN REVIEW, REUTERS, YONHAP NEWS AGENCY