There is little information about Korean children’s secondhand smoke (SHS) exposure at home. This paperexamines the extent and determinants of their SHS exposure at home. A population-based random digit dialtelephone survey was conducted in 2002 with 500 adults in Seoul. We analyzed data for 207 adults with childrenliving in the household. Thirty-one percent of respondents reported children’s SHS exposure at home. Themean weekly dose was 5 cigarettes among exposed children. Multiple logistic regression results showed thatchildren’s odds of SHS exposure at home increased if the respondent or spouse smoked, if the respondent’sparent smoked, if smoking was allowed in the home, and if fewer groups discouraged smoking. Stronger protectivemeasures are urged, such as widespread increase in home smoking bans and discouragement of smoking.