The aim of the present study was to investigate the role of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) in the diagnosis of post-transplant lymphoproliferative disorder (PTLD), a serious complication of solid organ and bone marrow transplant. Between January 2004 and January 2012, 40 patients (22 males; median age 52 ± 17.4 years, range 11-77 years) underwent (18)F-FDG PET/CT scans in our department for diagnostic evaluation of PTLD. Twenty-three (57.5%) patients had negative (18)F-FDG PET/CT and 17 (42.5%) had a positive examination. In five patients PET/CT revealed extranodal disease (adrenal, pleural, spleen, liver, lung, esophagus and bone involvement). On the basis of our results, (18)F-FDG PET/CT had a sensitivity of 88.2% (95% confidence interval [CI] 0.62-0.98), a specificity of 91.3% (CI 0.70-0.98), a positive predictive value of 88.2% (CI 0.62-0.98) and a negative predictive value of 91.3% (CI 0.70-0.98). The diagnostic performance of CT in patient-based analysis was: a sensitivity of 87.5% (CI 0.60-0.97), a specificity of 88.8% (CI 0.64-0.98), a positive predictive value of 87.5% (CI 0.60-0.97) and a negative predictive value of 88.8% (CI 0.64-0.98). PET/CT in five cases revealed more findings than CT, upstaging the disease, and revealed three extranodal findings, not visualized in conventional imaging. (18)F-FDG PET/CT plays a significant role in the setting of PTLD diagnosis, demonstrating its high accuracy in detecting PTLD.