Differential diagnosis in often difficult because of mixed symptoms and high comorbidity of psychiatric disorders in childhood and adolescence. This study examined the Rorschach oral dependency scale(ROD) among depressive disorder, bipolar disorder, attention deficit hyperactivity disorder(ADHD) based on the theoretical background that i) depression and bipolar disorder rooted in the fixation at oral stage and ii) ADHD is related to the malfunctioning from a neurological perspective. Only subjects who were correspondingly diagnosed as 'depressive disorder, bipolar disorder, and ADHD' respectively by a child psychiatrist and clinical psychologist were included in this study. The subjects were divided into the following group：17 people in the depressive disorder group, 16 people in the bipolar disorder group, and 17 people in the ADHD group. An ANCOVA was conducted in order to compare the ROD score differences among the three groups while controlling the main effects of the age factor. The results showed significant differences in the ROD scores among the different groups. Furthermore, results of the Bonferroni test showed depressive disorder had a higher ROD score than ADHD. In this regards, this study empirically proved the diagnostic utility of the Rorschach Oral dependency scale(ROD) in diagnosing pediatric disorders. Additionally, limitations of the study and proposals regarding follow up studies are also discussed.