Inappropriate use of medicines increases the risk of hospital admissions for the elderly. Not only does this lead to unnecessary suffering for the patients but also incurs a great financial cost to the society. A medicine decision support system in a Personal Digital Assistant (PDA), with a barcode reader, can provide an overview of the patients' complete medicine use, and detect unsuitable drugs and drug combinations. Focusing on the elderly, our aim was to evaluate if a mobile medicine decision support system with a barcode reader is useful and user-friendly for nurses in home care. The participants received a comprehensive overview from the patients' medicine use and noted drug-drug interactions, therapeutic duplications and warnings for drugs unsuitable for elderly people. The nurses regarded that the decision support system increased prevention and safety, was useful and user-friendly. Our findings suggest that most of the content and functions were regarded as important. Therefore, this decision support system might be a useful tool for district nurses.