Lhermitte-Duclos Disease (LDD) is a rare cerebellar lesion that has long been controversial as to whether the entity is a hamartoma, a malformation, or a neoplasm. Recent advances in metabolic imaging and molecular biology have unveiled biological features of LDD and a close relationship between LDD and Cowden disease. Adult onset LDD is now considered identical to Cowden disease in a US guideline. We present a case of LDD, in which high fluorodeoxy glucose (FDG) uptake was shown on PET/CT. We performed dual time point scans, in which a delayed scan exhibited more intense FDG uptake by the hamartomatous lesion than an early scan. We must remain aware of the possibility of LDD when intense accumulation is observed in a cerebellar lesion on FDG-PET/CT imaging.