this cross-sectional study was performed with 147 children with a medical diagnosis of asthma admitted to a public children's hospital in fortaleza, cerará (ce). the objective of the study was to analyze the accuracy of the defining characteristics of the nursing diagnosis "ineffective airway clearance" in children with asthma. a physical examination checklist was used for data collection. the most frequent defining characteristics were adventitious respiratory sounds (82.3%), dyspnea (55.8%), and changes in respiratory rate (50.3%). the nursing diagnosis "ineffective airway clearance" was present in 55.8% of the sample. the defining characteristic with the greatest sensitivity was "adventitious respiratory sounds". the specific characteristic for this diagnosis was "wide eyed". regarding the predictive values, adventitious respiratory sounds showed a high negative predictive value. in conclusion, studies that contribute to defining the most common defining characteristics for a particular population should be encouraged, as they serve as a guide for the practice of nursing.