Background: A huge portion of health expenditure is attributed to hospital services. Thus, it is important to use the resources appropriately. Many studies have measured inappropriate admissions and hospitalizations. The aim of this study was to review them systematically and determine the pooled quantity as well as the reasons behind such admissions and hospitalizations.Methods: PubMed, Scopus, Web of Science, Google scholar, and internal databases such as Sid, Magiran, and Barkat were searched in January 2018. Moreover, the grey literature was also performed. All studies which had assessed the appropriateness and inappropriateness of services were included. Newcastle-Ottawa scale was used for quality appraisal. I2 test, subgroup analysis, metaregression, and sensitivity analysis were performed. STATA was used for analysis. There was neither time limitation nor language limitation. The registration number in PROSPERO is CRD42019123401.Results: Of 1576 studies, 15 met the inclusion criteria. The number of medical files ranged from 198 to 1815. Most of the studies ( 14) were performed in teaching hospitals. AEP was the most frequent tool for assessing inappropriateness of the services. The pooled inappropriate admission and hospitalization were 11% (95% CI= 8% -14%)) and 13 % (95% CI= 10%-16%)), respectively. The most important determinants for inappropriate hospitalizations were attributed to physicians. Conclusion:A huge portion of health care services is inappropriate. Thus, it is highly recommended to monitor physicians more than before, as the more they are monitored, the less inappropriate the delivered services will be.