PURPOSE: The purpose of this study was to determine the important factors on juvenile delinquency and to examine relationships between sex, age, the family environment, the personality of adolescents, smoking, and juvenile delinquency. Methods: Data collection was done through questionnaire surveys. The subjects for this study consisted of 1,948 adolescents delinquents : 784, students : 1,164 in Korea, using proportional stratified random sampling method. Statistical methods employed were chi-square, t-test and path analysis. Results: The results of this study were as follows : 1. The delinquent adolescents were reared in a more dysfunctional family environment, and had a higher maladaptive personality than the other student adolescents. 2. The delinquent adolescents showed the larger amount of smoking than the student adolescents. The cause of increased smoking tendency among delinquents simply were 'for social relation', 'for diversion', 'for nicotine addiction', whereas 'for tension relieving' among non-delinquent adolescents. 3. The most powerful contributors on delinquent behavior were antisocial personality tendencies, smoking, sex, strength of parent- child relationships, and the age of the adolescents in this order. Conclusions: Our cross-sectional findings indicate that smoking was one of the most powerful contributing variables to delinquent behavior, but family environment, personality, sex and age of adolescents were also proved to be strong exogenous variables to smoking in adolescents.