The purpose of this study was to identify clinical and laboratory parameters that may improve the effectiveness of the use of fluorodeoxyglucose positron emission tomography ((18)F-FDG PET)(/CT) for diagnosing large vessel vasculitis (LVV), and secondarily to assess the contribution of (18)F-FDG PET/CT in finding other diagnoses for patients without signs of LVV on the scan. A multicenter retrospective study of (18)F-FDG PET(/CT) scans performed between January 2000 and December 2009 for clinical suspicion of LVV was conducted. A total of 304 (18)F-FDG PET(/CT) scans were included, of which 62 (20%) were positive and 242 (80%) were negative for LVV. Univariate analysis showed that patients with a positive scan were older (65.9 ± 13.4 versus 58.6 ± 16.5 years, p = 0.002), were more frequently female (76% versus 55%, p = 0.002), more often had a history of temporal arteritis (10% versus 3%, p = 0.044), less frequently had artralgia (31% versus 67%, p = 0.000), and had higher thrombocyte counts (434 ± 161 versus 373 ± 168 × 10(9)/l, p = 0.049) and a higher erythrocyte sedimentation rate (ESR) (72.6 ± 31.0 versus 51.4 ± 30.5 mm/h, p = 0.001) than patients with a negative scan. In the multivariate analysis, only artralgia (OR 0.091; 95% CI 0.023-0.366) and ESR (OR 1.024; 95% CI 1.002-1.046) remained statistically significant predictors. The presence of artralgia is a statistically significant negative predictor and an elevated ESR a statistically significant positive predictor of LVV showing up on (18)F-FDG PET(/CT). A reliable prediction of the outcome of the scan, based on these two parameters, is not possible however. (18)F-FDG PET(/CT) allows early diagnosis of LVV and may discover occult inflammatory or neoplastic disorders.