What is Known and Objectives Potential inappropriate medications (PIMs) can increase the risk of medication-induced harm. However, there are no studies regarding PIMs in older and critically ill patients with cardiovascular diseases in China. Therefore, studies evaluating PIMs in these patients can help in the implementation of more effective interventions to reduce the risk of drug use. Our objective was to analyse the prevalence of PIMs in elderly patients admitted to the cardiac intensive care unit (CICU) comparing the 2019 Beers criteria (Beers criteria), Screening Tool of Older People's Potentially Inappropriate Prescriptions (STOPP) criteria version 2 (STOPP criteria) and criteria of potentially inappropriate medications for older adults in China (Chinese criteria); and analyse the factors influencing the PIMs. Methods This cross-sectional and retrospective study was performed with elderly patients (>= 65 years) admitted to the CICU of the Beijing Tongren Hospital in China from January 2019 to June 2020. The PIMs were identified based on the Chinese, STOPP and Beers criteria at admission and discharge. The three criteria were compared using the Kappa statistic. Multiple regression analysis was used to investigate the influencing factors associated with PIMs. Results and Discussion A total of 369 patients who met the inclusion/exclusion criteria were included in this study. According to the three criteria used to evaluate the PIMs, the prevalence was 78.3% and 72.6% at admission and discharge, respectively. The prevalence rate of PIMs determined by the Chinese criteria was 62.1% at admission versus 56.6% at discharge (p = 0.134); the Beers criteria was 53.9% at admission versus 46.9% at discharge (p = 0.056); by the STOPP criteria was 20.6% at admission versus 13.8% at discharge (p = 0.015). Moreover, 28.9% (STOPP criteria), 56.8% (Beers criteria) and 73.4% (Chinese criteria) of patients taking PIMs on admission still had the same problem at discharge. The most common PIMs screened by the Beers, STOPP and Chinese criteria were diuretics, benzodiazepines and clopidogrel, respectively. Besides, the three criteria showed poor agreement. Finally, the stronger predictor of PIMs was the increased number of medications (p < 0.05). What is New and Conclusion The prevalence of PIMs in elderly patients admitted to the CICU was high. The Chinese, STOPP and Beers criteria are effective screening tools to detect PIMs, but the consistency between them was poor. The increased number of medications was a significant predictor of PIMs.