The rapid growth of mobile advertising offers advertisers greater communication opportunities to consumers. The ad platform is moving toward the mobile application from the web site. Despite potential capabilities of smart phones as a useful advertising tool, privacy concern toward ad messages has been an obstacle for adopting of mobile advertising widely. The situation is getting worse due to recent leakage of consumer information from major credit cards and banks in Korea. The purpose of this study is to demonstrate the relationships among several factors regarding smart phone usages--smart phone using time, smart phone dependency, mobile applications, privacy concern and mobile ad avoidance. The results of the study show that age is negatively correlated with using hours and dependency on smart phones, usages and attitudes toward smart phone applications. However, age turns out to be not a major factor regarding privacy concern and mobile ad avoidance. Those who are high in need for cognition tend to use more smart phone applications, show more favorable attitudes toward applications and higher mobile ad avoidance. Using time of smart phone is positively correlated with its dependency, number and attitudes toward applications. The higher smart phone dependency, the more favorable attitude toward applications as well. Those who are high in privacy concern tend to be high in mobile ad avoidance. The interaction effect of age and need for cognition on smart phone dependency turned out to be significant. While those who are high in need for cognition showed a constant level, those who are low in need for cognition showed high dependency on smart phone before the age of 40, however, smart phone dependency decreased sharply after 40.