¹⁸F-fluoro-2-deoxyglucose (FDG)-based positron emission tomography (PET)/computed tomography (CT) is an indispensable tool in modern oncology, extensively used for diagnosing and staging various cancers. The maximum standardized uptake value (SUV_max) of FDG helps identify the most metabolically active areas of disease. In this analytical cross-sectional study performed between January and December 2019, we compared SUV_max for different cancer types and determined the effect of demographic, pathological, and clinical variables on SUV_max. The study included 117 newly diagnosed cancer patients who underwent FDG PET/CT before treatment. Data on descriptive variables, including age, gender, stage, histopathological diagnosis, and tumor differentiation grade, were collected for each patient. Correlation analysis of these variables with SUV_max in FDG PET/CT was performed using Spearmen’s test and a forward stepwise regression model. A total of 117 patients (63 males and 54 females) with a median age of 61 years (range: 21 – 90) were included in this study. Histopathological diagnoses revealed squamous cell carcinoma (n = 71%), adenocarcinoma (n = 24%), and small cell cancer (n = 5%). The SUV_max of the primary tumor was positively correlated with histology (P < 0.05), with the highest SUV_max observed in squamous cell carcinomas. In conclusion, SUV_max was positively correlated with histology, while no association was detected with the patient’s age and gender, as well as the stage, organ, site, or grade of the tumors. However, we recommend a larger and more homogenous study sample to further investigate any clinically relevant relationship between the SUV_max and various disease factors in diverse patient populations.