OBJECTIVE Deep sternal wound infection (DSWI) is a refractory complication after heart surgery, and debridement is the first-line treatment. The accurate identification of the extent of the infection is the key to successful debridement. The present study assessed the diagnostic accuracy of fluorine-18 deoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) for identifying the infected area of DSWI. METHODS Between February 2015 and May 2017, 73 consecutive patients with suspected DSWI received 18F-FDG PET/CT examinations before their operation. The PET/CT and extracted CT images were analyzed by nuclear medicine physicians and radiologists to determine whether the sternum, mediastinum, vascular prosthesis, and each costal cartilage were infected. All the patients received debridement and chest wall reconstruction within 1 week following the PET scan. The final diagnosis was on the basis of surgical, microbiological, and histopathological findings. RESULTS Of the 73 patients, 64, 54, 28, and 6 patients were diagnosed with sternal osteomyelitis, mediastinitis, costal chondritis, and vascular graft infection (VGI), respectively. The sensitivities of PET/CT for diagnosing sternal osteomyelitis, mediastinitis, and costal chondritis were 98.4%, 77.8%, and 100.0%, respectively, and the corresponding specificities were 94.7%, 82.1%, and 100.0%, respectively. PET/CT correctly diagnosed all six cases of VGI. There were 65 infected costal cartilages in the patients with costal chondritis. The sensitivity, specificity, and accuracy of PET/CT for locating infected costal cartilages were 81.5%, 99.8%, and 98.6%, respectively. CONCLUSIONS PET/CT proved to be a useful tool for determining the depth of DSWI and for locating infected costal cartilage; therefore, this tool can help guide debridement.