Positron Emission Tomography (PET) is an important cancer imaging tool, both for diagnosing and staging, as well as offering predictive information based on response. PET is a nuclear medicine imaging technique which produces a three-dimensional image of functional processes in the body. While PET is commonly used to detect the tumors, especially in breast, colon, lung and for lymphoma, as well in the last decade it is verified as considerably more accurate than Computed Tomography (CT) in the distinction between benign and malignant lesions. PET is not only more accurate than conventional imaging for the assessment of therapy response, but also it is useful to detect some viable tumor cells after treatment. However, motion is a source of artifacts in the medical imaging and results in reducing the quantitative and qualitative accuracy of the image. In general during the procedure of PET scanning, a few types of motion can occur that should be corrected and compensated. Different body motions are classified as brain motion, cardiac motion and respiratory motion. In this study, some of the most important motion correction and compensation methods using PET imaging system are compared.