Objectives Patients' own drugs (PODs) are the medicines that patients have obtained in the community setting and bring to hospital. Little is known about the frequency with which patients bring PODs when admitted to hospital and the quality of these drugs has not been well investigated. The purpose of this study was to evaluate the quantity and quality of the PODs brought to hospital during admission. Methods Clinical pharmacists in four wards at three different hospitals evaluated the quantity and quality of PODs. The quantity of PODs relates to the number of patients who brought one or more of their medicines to hospital and the total number of PODs. The quality of PODs was evaluated by assessing the appearance, container, labelling, identification of contents, storage conditions and expiration, and thereby the usability of the POD. Results From March 2010 to July 2011, 4600 drugs from 529 patients were assessed. In total, 59% of patients took PODs to hospital and 43% (n=1985) of drugs from patients' medication histories were brought to the hospital. The majority of PODs were usable (58.6%, n=1164) but most were unnecessary (52.3%, n=1039) because substitution was possible. In total, 92.5% (n=1836) of all PODs were not used during admission, although 33.5% (n=615) of these added information to the patients' medication history. Conclusions More than half of patients brought PODs to hospital which gave the advantage of providing medication history. The majority of PODs were suitable for use in hospital. Only 7.5% of all PODs were actually used because substitution to generic or equivalent drugs from the hospital's formulary was preferred.