Rosai Dorfman disease (RDD) or sinus histiocytosis is a rare non-neoplastic idiopathic disease characterized by massive lymphadenopathy in young adults. Extranodal involvement is seen in 25%–43% cases. RDD is usually self-remitting. However, it mimics lymphoproliferatve disorders clinically as well as on imaging. We present the 18F-FDG PET/CT findings in a 46-year-old female patient with nodal RDD.