Objective: to evaluate the resistance and pressure of the lips in Class I, II and III Angle’s malocclusion subjects, in comparison to reference values and relate them with gender and age. Methods: a quantitative, descriptive and cross-sectional study. Participants included 40 subjects, 20 women and 20 men, average age 26.3 years, separated by occlusal classification. The volunteers answered on the self-reported performance of the stomatognathic functions and were submitted to the evaluation of the mobility and posture of the lips. Pressure and resistance were measured with the Iowa Oral Performance Instrument (IOPI) and the results compared to the reference values described in the instrument´s manual. The data were analyzed descriptively and, for inferential analysis, Pearson's Chi-Square test was used. The significance level was considered 5%. Results: a decrease in pressure and resistance values wasobserved in all patients, including Angle’s class I group. There was an inverse relationship between the age of the subjects and the values of pressure of lips with statistical significance (p = 0.02). In general, women had lower pressure values than men. Conclusion: all study subjects had lower pressure of the lips than the reference values described in the literature.