Abstract: The standardized uptake value (SUV) and the ratio of lesion's counts to background counts (L/B) are usually used in clinical oncology. L/B is mostly used for dual-head coincidence detection system. SUV is widely used for dedicated PET in differentiating the benign and the malignant, tumor staging, evalu-ating therapy response and predicting patient survival and disease-free interval. And some factors which should be paid attention to in clinical application are presented.