Thrombosis and inflammation are intimately linked. Inflammatory component of venous thromboembolism (VTE) may allow the use of FDG positron emission tomography / computed tomography (FDG PET/CT) in the detection of thrombotic process. Published studies remain limited and contradictory. We aimed at evaluating the performance of FDG PET/CT in the detection of VTE in a population of patients enrolled in a prospective study evaluating FDG PET/CT for cancer screening in etiological assessment of idiopathic VTE. The first consecutive 100 patients who underwent FDG PET/CT were included. Visual and quantitative analyses of vascular axes was performed and compared with lower limb veins compression ultrasonography, lung scintigraphy and/or computed tomography pulmonary angiography. Out of the 100 patients, 63 presented lobar pulmonary embolism for a total of 217 embolic sites and 62 had a deep vein thrombosis for a total of 143 thrombotic sites. Regarding pulmonary embolism, sensitivity and specificity of FDG PET/CT were 3% (95%CI: 1-6%) and 99% (95%CI: 98-100%). SUV max ratio between pulmonary embolism location and non-pathological contralateral vessel was 1.04±0.18 (p=0.7). Regarding deep vein thrombosis, sensitivity and specificity were 31% (95%CI: 24-39%) and 88% (95%CI: 81-92%). The metabolic activity was significantly higher than in contralateral vessels (p<0.001), with a SUV max ratio of 1.25±0.53, but without any significant SUVmax threshold applicable in routine practice for deep vein thrombosis diagnosis. FDG PET/CT is not accurate enough for the diagnosis of VTE.