Background/Aim. There are no recommendations for the optimal nutritional status assessment parameters (NSAPs) in the current literature. The aim of this study was to define the optimal NSAPs for nutritional status assessing in gastroenterological patients on hospital admission. Methods. Nutritional status of 612 gastroenterological patients was evaluated at the admission using 6 NSAPs: unintentional weight loss (WL), body mass index (BMI), triceps skinfold thickness (TSF), mid-upper arm muscle circumference (MAMC), serum albumin concentration (ALB), and lymphocyte counts (LYM). According to their nutritive status, the patients were classified as well nourished (normally nourished and obese), moderately undernourished and severely undernourished. Based on the similarities and differences in the assessment results, obtained according to each of 6 parameters, the optimal nutritional assessment parameters were defined, separately for the well-nourished / undernourished patients and for moderately / severely undernourished patients. Results. The incidence of malnutrition was in the range 5.9-29.7%. The results based on MAMC, ALB, and LYM were similar (25.2- 29.7%; p > 0.05), while the results based on WL, BMI, and TSF differed significantly (5.9-19.9%; p = 0.001-0.015). The assessment based on BMI was the most severe criterion, while the assessment according to MAMC was the mildest criterion in selection of malnourished patients. The assessment according to MAMC was the mildest criterion for the selection of severe malnourished patients (severely malnouorished patients accounted for 70.l%), while BMI and LYM were the most severe criteria (severely malnouorished patients accounted for 22.2% and 27.3%, respectively). The results based on BMI and LYM were similar (Wilcoxon test; p > 0.05). Conclusion. Combining BMI with MAMC is sufficient for the assessment of the nutritional status of gastroenterological patients on admission, as well as for differentiation between severely malnourished and moderately malnourished patients. .