Kim Suna was born in Daegu and then spent much of her school years in Chōfu, Tokyo (she speaks Japanese fluently). After first appearing in a music video by Kim Hyun-cheol, she started appearing often on TV but did not emerge as a star. She would first become well known as a film actress, debuting in the big-budget box office failure Yesterday but going on to play a lead role as a student teacher in the unexpected hit Wet Dreams.
Following this, Kim began to establish a niche for herself in comedies, often appearing as a straight-talking and not particularly demure comic heroine. She appeared in three films in 2003: a memorable cameo appearance in the period comedy Once Upon a Time in a Battlefield, opposite Im Chang-jung in the strong hit The Greatest Expectation, and together with Cha Tae-hyun in the little-watched Happy Ero Christmas. In 2004 she took the lead role in S Diary as a jilted woman who decides to get revenge on her ex-boyfriends.