Introduction: The purpose of the present study is to compare Brain/Behavioral systems in social anxiety, shyness with social anxiety symptoms, and shyness without social anxiety symptoms.Method: 1800 high school students in Kermanshah completed the Stanford Shyness and Social Anxiety questionnaires. Firstly, according to the gained scores, 215 subjects were selected as shy and 105 subjects were selected as social anxiety disorders. Afterwards, among the 105 nervous people 60 were selected based on the DSM-IV-TR interview. By performing the SPIN questionnaire again on the 215 shy sample and also interviewing them once more, two shy groups with/without anxious symptoms were selected. In the end, all the subjects of each group (each group 60 people) completed the Jackson-5 questionnaire.Results: Fight, flight, and freeze with social anxiety symptoms was much higher in the shy group compared to the social anxiety group. Although BIS in the social anxiety group was higher compared to the shy group without social anxiety symptoms, fights were meaningfully higher in the shy group without social anxiety symptoms compared to social anxiety group. The comparison between the two shy groups showed that the shy group with social anxiety symptoms had more BIS, flight and freeze behaviours compared to the shy group without social anxiety symptoms.Conclusion: Also, the shy group without social anxiety symptoms showed higher BIS and fighty activities.