AbstractPURPOSE. To clarify the use of two nursing diagnoses, activity intolerance and impaired physical mobility, with elderly patients.METHOD. Ninety‐two elders from a long‐term care facility in Wonju, Korea. A checklist developed by the researchers was used for data collection.FINDINGS. Defining characteristics from this study related to psychological components of activity intolerance are significant in differentiating between the two diagnoses. Using a decision‐making tree based on data from this study, each nursing diagnosis can be correctly identified.CONCLUSIONS. The results of this study are significant in broadening the defining characteristics to be used in differentiating between two nursing diagnoses.PRACTICE IMPLICATIONS. Clarification of nursing diagnoses serves to direct students and nurses to choosing appropriate interventions.