PURPOSETo determine the utilization of nursing diagnoses by nursing students and their ability to formulate the NANDA nursing diagnoses under the functional health patterns to evaluate whether there is a link between documented nursing diagnoses and patients' assessment data.METHODSData were obtained from the standardized nursing assessment forms and care plans documented by 57 nursing students in a pediatric nursing course. A total of 569 care plans were documented for patients (children and their families).FINDINGSFor 569 children in 3 different pediatric clinics, 70 different nursing diagnoses were documented. Some of the nursing diagnoses were used in various frequencies for a total of 3,433 documented diagnoses in Nutrition‐Metabolic (n= 1,274), Activity‐Exercise (n= 594), Cognition‐Perception (n= 572), Role Relationships (n= 330), and Health Perception‐Health Management (n= 327) Health Patterns. The most frequently occurring NANDA diagnoses were knowledge deficit (n= 275), altered nutrition: less than body requirement (n= 265), risk for altered body temperature (n= 263), anxiety (n= 236), and altered comfort (n= 227).CONCLUSIONSThe majority of the students had adequate knowledge and ability to formulate nursing diagnoses according to NANDA, but documented diagnoses were not always supported by patients' assessment information. This might be a result of the inadequate diagnostic reasoning and teaching methods used, and being introduced to the diagnostic process for the first time in this course. Ultimately, consistent expectations and using the classification systems will lead to competency in diagnostic reasoning.