The purposes of this study are to secure the desirable parent-adolescent cohesion, to find out the real parent-adolescent cohesion and to investigate the influences of family structure variables on the parent-adolescent cohesion. The data are obtained from a sample of 364 high school students in Seoul by using questionaires. X2-test, t-test, one-way ANOVA, Scheffe-test, Kruskal-Wallis test and difference of percentages with cross tabulation are used for data analysis. The major findings are as follows : 1) The high parent-adolescent cohesion is found to be desirable. 2) The mother-adolescent cohesion is higher than that of the father-adolescent. 3) The father-son cohesion is influenced by siblings existence, while the mother-son cohesion is influenced by siblings existence and birth order. The father-daughter cohesion is influenced by birth order and difference of age between mother and daughter. However the mother-daughter cohesion is influenced by the presence of the arents and difference of age between mother and daughter. 4) The results discribed in 3) are changed considerably by controlling the open-communication variable.