Background/aim: The present study aimed to assess the relationship between the maximum standardized uptake value (SUVmax) on 18 F-fluorodeoxyglucose positron emission tomography computed tomography ( 18 F-FDG-PET/CT) and the geriatric nutritional risk index (GNRI) in patients with soft-tissue sarcomas (STSs)., Patients and Methods: The present single-center retrospective observational study included patients who underwent 18 F-FDG-PET/CT and for whom serum albumin levels, height, and body weight were measured prior to therapeutic intervention., Results: A total of 81 patients were included in the study. The mean SUVmax was 11.1±9.9. The 5-year overall survival (OS) and disease-free survival (DFS) rates were 79.7% and 52.4%, respectively, for the higher SUVmax group (≥11.1) and 91.0% and 73.0%, respectively, for the lower SUVmax group (<11.1). For the GNRI, the 5-year OS and DFS rates were 89.6% and 64.3%, respectively, for the negative-risk group, and 73.3% and 77.1% for the positive-risk group, respectively, with no significant differences. The mean SUVmax was 9.7±8.1 and 19.1±14.9 for the negative- and positive-risk groups, respectively. The positive-risk group had a significantly higher SUVmax than the negative-risk group (p=0.03). Furthermore, there was a negative correlation between the SUVmax and GNRI (r=-0.48, p<0.05)., Conclusion: A higher SUVmax and lower GNRI in patients with STS may contribute to a poor prognosis. The deregulatory elevation of tumor glucose metabolic activity may affect serum albumin levels and weight loss in patients with STS, resulting in a decrease in the GNRI., (Copyright © 2025 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)