This study examined the effects of paternal smoking on the developmental levels of children younger than 3 years of age. For this purpose, the paper made use of data from the Panel Study on Korean Children which has been released in 3 waves - 2008, 2009, and 2010. The main findings are as follows. First, the smoking characteristics of parents (e.g., the amount of smoking in the morning, the time starting the first cigarette of the day) rather than the duration of smoking or whether the father smoked or not revealed significant relationships with developmental levels. Second, children whose fathers preferred smoking in the morning exhibited lower activity levels or more areas with developmental delays than did their counterparts. Third, children whose fathers smoked more than 11 cigarettes a day were more likely to show problematic developmental levels, especially among those whose fathers responded so only for 1 year out of 3 years. Based on these findings, this study suggests that future research may be conducted, relating to the mechanisms through which morning smoking affects children and possible interventions for such morning smokers.