This cross-sectional study was performed with 151 children inpatients of a pediatric hospital in Northeastern Brazil, with the objective to analyze the accuracy of the defining characteristics of the diagnoses ineffective airway clearance in children with acute respiratory infection. A thorough respiratory evaluation was performed and the diagnostic inference was developed by specialists. The most frequent defining characteristics were adventitious breath sounds, ineffective cough, dyspnea, and changes in respiratory rate. Ineffective airway clearance was present in 37.7% of the sample. Agitation was the characteristic with the highest sensitivity. Dyspnea, adventitious breath sounds, orthopnea, changes in respiratory rate and agitation presented higher specificity for the diagnosis. In conclusion, the defining characteristics showed different performances to correctly classify children with infective airway clearance. Studies like this can contribute for a correct nursing diagnostic inference and for the implementation of more effective interventions, thus improving the quality of health care. Descriptors: Respiratory Tract Infections; Nursing Diagnosis; Child.