The study aimed to assess the prevalence of the frailty syndrome in older patients hospitalized in the geriatric ward depending on the diagnostic criteria used, the feasibility of particular diagnostic scales in hospitalized patients, and their compatibility. Material and methods: Patients admitted to the Department of Geriatrics of Hospital of the Ministry of the Interior and Administration in Bialystok within eight months were included in the study. Four diagnostic scales were used to identify the frailty syndrome: Fried criteria, 7-point Clinical Frailty Scale (CFS), 40-item Frailty Index (FI), and FRAIL Scale. The compatibility of the scales was determined using Cohen's Kappa statistics. Results: 416 patients (mean age 81.2 ± 6.91 years, 77.4% women) were included in the study. Depending on the scale, the prevalence of frailty syndrome varied from 26.8% ( FRAIL Scale), 52.3% (Clinical Frailty Scale), and 58.1% (Fried criteria) up to 62.9% (Frailty Index). We observed the highest feasibility for CFS (100%), intermediate for Frailty Index (95.2%), FRAIL Scale (89.7%), and the lowest for Fried scale (79.8%). The highest level of agreement was found between the CFS and Fried scale, with 70.2% consistent ratings (Cohen Kappa 0.49). Conclusions: Patients in the geriatric ward are characterized by a high prevalence of frailty, although it differs depending on the criteria. The Frailty Index found the highest prevalence and the lowest in the case of the FRAIL scale. The feasibility of scales and their comparability differed; the most difficult to use in daily practice was the Fried scale, while the Clinical Frailty Scale was determined feasible in all patients. The highest agreement was observed between the Fried criteria and the Clinical Frailty Scale and the lowest between the FRAIL scale and the remaining ones.