Introduction: Changes in body composition have important implications for the health status and functional efficiency of the elderly. There are many different methods used to diagnose malnutrition, with BMI being used most frequently. Purpose: The objective of this research was to analyse the nutritional status of over 65 year olds using different BMI ranges and verify if the BMI cut-off values for the elderly are justified. Materials and methods: The study population consisted of people aged 65 years and over, hospitalized in selected medical and care institutions located within the Bielsko county. Information was compiled by a questionnaire and the research was conducted by a direct interview. Anthropometric measurements (weight, height, BMI) were taken and clinical data were obtained from review of the participants’ medical charts. Results: In total, 202 people took part in the study. The majority of the study population were women (73.76%). The average age of participants was 77.59 ± 7.35 years. The average length of stay was 3.16 ± 2.48 days (hospitalized patients) and 66.17 ± 55.64 months (residents of care institutions). The majority of participants (86.63%) suffered from multiple diseases. The average BMI of the surveyed was 27.76±5.34 kg/m2. According to WHO recommendations, 24.75% of participants were classified as having a “desirable” BMI, whereas 71.29% of them exceeded the “desirable” BMI range. BMI analysis in accordance with criteria proposed by the Committee on Diet and Health classified 38.61% of participants as having a “desirable” BMI, 39.11% as overweight or obese and 22.28% as being underweight. Conclusions: Our study showed that BMI range for elderly were more effective in detecting of under nutrition in study population. However, more researches are needed to define specific BMI cut-off points for elderly and, once defined, these standards should be applied as international standards.