A retrospective review was performed of 14 patients with mycobacterial granuloma that was resected at Kanagawa Cancer Center Hospital from April 2006 to September 2012. Computed tomography findings and the maximum standardized uptake value (SUVmax) determined by 2-[¹⁸F]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) were retrieved from the patients' medical records. The causative pathogen was identified in eight patients by using polymerase chain-reaction assays; it was found to be Mycobacterium tuberculosis in one patient and Mycobacterium avium in seven. The median SUVmax was 2.93 (range, 0-6.23). Of 9 patients (64.3%) with positive PET findings (SUVmax≥2.5), tumor size was <20 mm in 2 patients (33.3%) and ≥20 mm in 7 (87.5%). The frequency of positive PET findings tended to be greater among patients with tumors ≥20 mm in size (p=0.091). The volume doubling time of all 3 nodules with positive PET findings of 6 nodules followed up more than 2 months was less than 200 days. In this series, most of the mycobacterial granulomas with a size ≥20 mm were associated with positive PET findings. The mycobacterial granulomas with positive PET findings could show rapid growth similar to lung malignancy, which may lead to difficulties in distinguishing between lung cancer and mycobacterial granuloma by using FDG-PET alone.