Abstract: PET scanning has a definite clinical impact on diagnosis, initial staging, restaging, monitoring therapeutic effects of malignancies, and on assessment of myocardial viability. Whereas, PET scans has false positive diagnosis and false negative diagnosis of malignant lesions, It leads to reduce specifity in PET imaging. Application of diagnostic CT, especially applying contrast enhanced CT scans, three dimensional technique, CTA(CT angiography), CT perfusion and CT virtual endoscopy can realize dominance complementation with PET and CT, PET-CT imaging diagnosis combines with PET and CT diagnostic technique, It improves sensitivity, specifity, and accuracy in clinical application of PET-CT scanner.