Anxiety disorders represent one of the most common and debilitating forms of psychopathology in children and adolescents. A way to prevent from a bad prognosis is to develop assessment tools that are able to identify the anxious phenomenon as soon as possible, at any time or culture. Objective: To evaluate the anxiety levels in children and adolescents from Rio de Janeiro. Method: Using a clinical sample of 48 outpatients and a community sample of 269 children and adolescent (8-16 years old) who lived in Rocinha and other localities, the MASC-BV and other psychometric tools were completed. Results: The MASCBV exhibited strong internal reliability, demonstrated good discriminative validity, good convergent validity and good criterion validity. The results are comparable to those presented in the validation study of the MASC in Brazil and to the first studies of the scale. As expected, high levels of anxiety symptoms were found in girls. Not expected, the higher scores in MASC-VB in the sample from Rocinha. Conclusion: The MASC is one of the most world-wide used scale to measure anxiety in children and adolescents. The results indicate good psychometric properties that shows it can be a useful measure to Brazilian population. New studies are necessary to better understand the high levels of anxiety in the community sample, specially in the Rocinha group.