OBJECTIVES: This study aimed to investigate the association of diffuse splenic F-18 fluorodeoxyglucose (FDG) uptake on positronemission tomography/computed tomography (PET/CT) with tumor maximum standardized uptake value (SUVmax), presence of distantmetastases, and hematological and inflammatory parameters.MATERIAL AND METHODS: Initial FDG PET/CT of 15 lung cancer patients with diffuse splenic FDG uptake were retrospectively analyzed(Group 1). Twelve patients who recently underwent FDG PET/CT for histopathologically proven lung cancer were enrolled as thecontrol group (Group 2). All 27 patients had hematological data, including C-reactive protein (CRP) level, within 5 days before or afterPET/CT. To determine SUVmax, the region of interests included the tumor, liver, spleen, and iliac crest. The possible associations betweenthe spleen/liver (S/L) and bone marrow/liver (BM/L) ratios and tumor SUVmax, presence of metastasis, and hematological parameterswere evaluated.RESULTS: The S/L ratio and hemoglobin (Hb) levels were different between the two groups (p=0.000 and 0.05, respectively). The numberof patients with anemia were significantly higher in Group 1 than in Group 2 (p=0.02). Although mean Hb levels were different betweenthe two groups, there was no correlation between Hb levels and S/L ratios. There was no significant difference between the two groupswith respect to the numbers of patients who had an accompanying infection site. Only CRP levels were correlated with S/L ratios inGroup 1 among various other parameters (r=0.559, p=0.05).CONCLUSION: Our results suggested that inflammation degree correlated with increased splenic FDG uptake in lung cancer patientsand was enhanced by anemia. Systemic inflammation and anemia could be important causes of diffusely increased splenic FDG accumulationon PET/CT examinations of lung cancer patients.