Background: The Zung’s rating instrument for anxiety disorders has been used in several Colombian researches. Its internal consistency and factor structure have not been reported among university students. Objective: To calculate the internal consistency and explore the factor structure of three versions of the Zung’s rating instrument for anxiety disorders among university students. Method: Two-hundred and twenty-one medicine and psychology students of a private university in Cartagena, Colombia, completed the 20-item version of the Zung’s rating instrument for anxiety disorders. The mean of age of students was 20.5 years (SD=2.6), 64.4% were women, and 54.3% studied medicine. Cronbach alpha was computed and exploratory factor analysis was done for the three versions. Results: The 20-item version of the Zung’s rating instrument for anxiety disorders presents Cronbach alpha coefficient of 0.77 and three principal factors accounted for 40.1% of the total variance. The 10-item version showed Cronbach alpha of 0.83 and two-dimensional structure responsible of 54.0% of the total variance. The 5-item version showed Cronbach alpha of 0.74 and one-dimensional structure accounted for 49.5% of the total variance. Conclusions: The 10- and 5-item version of the Zung’s rating instrument for anxiety disorders present better psychometric properties than the original 20-item version. It is necessary to estimate the properties of these versions compared with a gold standard.