The purpose of this study was to examine the relationship of maternal behavior and communication to the smartphone addiction proneness of preschoolers. Data were gathered from August 1 to 30, 2014. The subjects in this study were the selected preschoolers and their mothers who numbered 301. The preschoolers attended daycare centers and were at the western ages of three to five.The instruments used in this study were Parental Behavior Questionnaire, Communication Questionnaire and Smartphone Addiction Observation Scale. As for data analysis, a statistical package SPSS WIN 19.0 was employed to obtain statistical data on percentage, mean, standard deviation and Pearson correlation coefficients, and a hierarchical regression analysis was made. The VIF and DW coefficients were calculated before the regression analysis was carried out.The major findings of the study on the research questions were as follows.Concerning Research Question 1 about the maternal behavior and maternal communication of the mothers and the smartphone addiction proneness of the preschoolers, responsive behavior was the most common maternal behavior(4.27, SD=.53), and positive communication (4.02, SD=.54) was more prevailing than negative one(2.64 SD=.77). Thus, the majority of the mothers communicated with their children in a good way.Concerning Research Question 2 about the correlation of the maternal behavior and communication of the mothers to the smartphone addiction proneness of the preschoolers, the addiction proneness of the preschoolers became weaker in every subfactor when the mothers showed more boundary-setting maternal behavior.As to Research Question 3 about the influence of the maternal behavior and communication of the mothers on the smartphone addiction proneness of the preschoolers, positive maternal communication served to lower the smartphone addiction proneness of the preschoolers. In the case of negative communication, maternal boundary setting exerted the most significant influence on lowering the smartphone addiction proneness of the preschoolers. Rational guidance and responsive maternal behavior also were identified as major variables, but responsiveness was rather found to have strengthened the tolerance of the preschoolers.In terms of mother-child communication, negative communication had a significant impact on the entire smartphone addiction proneness of the preschoolers and every subfactor of it, and that was most influential. When the mothers guided their children in a more rational way, they had less negative communication with their children, and it was effective at lowering the level of addiction as well.The findings of the study illustrated that the maternal behavior and communication of the mothers were linked to the smartphone addiction proneness of the preschoolers. Therefore it's required to pay careful attention to the dysfunctional, negative use of smartphones among preschoolers, and how to educate them to refrain from unnecessary smartphone use should discreetly be devised. Also, the necessity of education about the negative influence of excessive smartphone use should be stressed to raise awareness of it.