OBJECTIVES: The aim of this study is to evaluate the bone scintigraphy (BS) and positron emission tomography (PET) in the early diagnosis of medication-related osteonecrosis of the jaws (MRONJ) and their possible use in the identification of patients at risk for MRONJ. MATERIAL AND METHODS: Thirty-one patients treated with ONJ-related drugs and who had undergone BS or PET for the evaluation of bone lesions were included in the study. The jaws of each patient were divided into four areas. For each area, the presence of pathological tracer uptake was evaluated and related to the eventual MRONJ development. Sensitivity, specificity, and predictive values of both techniques were determined. The latency from the finding of pathological tracer uptake in BS or PET to the clinical diagnosis of MRONJ and the odds ratio were also calculated. RESULTS: Sensitivity and specificity of BS for MRONJ prediction were, respectively, 83.3 and 87.5%. Positive and negative predictive values were, respectively, 73.2 and 92.8%. The odds ratio was 35. Sensitivity of PET was 33.3%, specificity was 94.9%, and positive and negative predictive values were 70.0 and 80.0%, respectively. The odds ratio was 9.333. All values were statistically significant. CONCLUSIONS: BS and PET may be accurate techniques for an early prediction of MRONJ.