As we believe it is an important problem in our environment, we determined the prevalence of potentially inappropriate medications (PIM) using the STOPP/START, Beers and PRISCUS criteria, and also determined the clinical variables related to the prescription of PIMs in older adults. It is a retrospective cross-sectional study in Geriatrics. Participants were all patients over 65 years discharged from the Internal Medicine Service of La Princesa hospital during February 2014. We measured inappropriate prescriptions detected with CheckTheMeds® computer tool. The study included 143 participants, mean age 87±7 years. Using Beers criteria, 421 PIMs were identified in 114 patients, with STOPP criteria, 277 PIMs were identified in 111 patients, with START criteria 279 PIMs were identified in 113 patients and using PRISCUS 47 PIMs were identified in 42 patients. Correlation between STOPP and Beers was 70%. An association between PIM prescribing and polypharmacy was detected with different criteria. CheckTheMeds® is a useful tool to improve detection and management of PIM in order to obtain evidence-based pharmacological treatment.