ntroduction: In the last decade, the prevalence of anxiety disorders has increased in children. Most of studies had surveyed the prevalence of these disorders symptoms in children and adolescents. However, there are few studies on factors influencing the expression and intensity of these disorders. Objective: Our aim in this study was to investigate the effects of demographic variables on children anxiety. Method: In this descriptive- comparative study, using multistage cluster sampling, 507 students were selected from 92249 students of third, fourth and fifth grade of public elementary schools in Mashhad . Multidimensional anxiety scale for children (MASC) and demographic characteristics questionnaires were used. Results: The MANOVA test showed that the effect of gender on anxiety is significant (p<0/001). Also, results demonstrated a significant difference in scores of physical symptoms, social anxiety and avoidance of harm between girls and boys. Except for the avoidance of harm component, boys’ scores were higher than girls in other components. The MANOVA test showed that the effect of grade on anxiety is significant (p<0/05). Furthermore, between the three grades of students, a significant difference was found only in the avoidance of harm component in which fourth and fifth grade students’ scores were higher than the scores of third grade students. Conclusion: Results showed that demographic variables have an effect on children\'s anxiety. For example: by increase in age and cognitive development, children develop more understanding of risky situations and try to avoid them. Therefore, they experience more worry and anxiety. Overall, the results of this study suggest that considering such variables as gender and age of children will facilitate diagnosis and treatment for therapists and counselors.

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