Abstract: The resistance of malignant tumors to chemotherapy is a major cause of treatment failure. One important mechanism in this resistance is the overexpression of adenosine triphosphate-binding cassette transporters. The best-characterize member of this superfamily of transporters is P-glycoprotein(P-gp). The qualitative and quantitative ananlysis of P-gp mainly depends on the tissue biopsy or postoperative pathologic tissue in vitro. It is important to find a method of noninvasive and dynamic monitoring tumor multidrug resistance. Many positron imaging agent of P-gp substrates and inhibitors have been researched, and part of them have been researched in clinic. In this review, the current status is summarized on PET imaging and P-gp function.