Objective To compare the efficacy of Conventional Chest Physical Therapy with Positive Expiratory Pressure in the treatment of cystic fibrosis patients during hospital treatment of exacerbation. Methods Randomized clinical trial with 29 patients at the Hospital de Clínicas de Porto Alegre. Thirteen patients were randomly assigned to Group A (Positive Expiratory Pressure) in which the seated patient went through 15 breathing cycles using a mask with a positive end-expiratory pressure of 13 cmH2O, followed by huffing without the mask along with coughing and expectoration. This sequence was repeated 7 times during 30 minutes. Sixteen patients were included in group B (Conventional Chest Physical Therapy) where patients assumed five postural dr...