The aim of our report is to demonstrate the complementary roles of bone scintigraphy (BS), magnetic resonance imaging (MR), and positron emission tomography using 2-deoxy-2-[18F]fluoro-D-glucose (F-18-FDG PET/CT) in the diagnosis and treatment monitoring of a child with primary non-Hodgkin’s lymphoma of bone (PLB). Increased blood flow, high tissue accumulation, and markedly increased uptake on the late BS pointed toward an active bone process in the left femoral region. Bone marrow infiltration of the left femur and cortical sclerosis, which were both demonstrated by MR imaging, were later confirmed as PLB by bone marrow biopsy. The normalizations of the flow and tissue phases of BS a year after treatment and during the entire follow-up were in keeping with inactive disease and clinical remission. However, even 8 years after treatment and complete remission, MR imaging demonstrated persistent unmodified bone marrow alteration and appreciable cortical involvement. A slightly increased metabolic activity of the left femoral epiphysis demonstrated by F-18-FDG PET/CT and mild activity in the same region on delayed BS were demonstrated in the late follow-up. Our results strongly suggest that BS and MR imaging should be included in the diagnostic algorithm of children with undefined bone symptoms. However, mild metabolic activity on the F-18-FDG PET/CT scan could not reliably differentiate between the presence or absence of disease in a patient with PLB in clinical remission.