This paper discusses theoretical considerations of ethics in building and using a text mining application in nursing documentation. Nursing documentation is based on the process of gathering information from the patient, setting goals for care, documenting nursing interventions and evaluating delivered nursing care. Privacy-sensitive health care documentation brings specific ethical concerns and difficulties that one needs to be aware of and conform to when developing and using text mining tools in electronic patient records. We discuss how patient confidentiality can be ensured in this domain and how text mining might support nurses to give better and more efficient care for their patients. Our conclusion is that text mining of nursing documents holds the promise of great benefits when the potential risks are taken into consideration.