Abstract: This paper is concerning on the NEMA Standard Publication NU 2-2001 of Performance Measurements of Positron Emission Tomographs, which is the revised edition of the NEMA Standard Publication NU 2-1994. Seven primary sections are included, such as: definitions, symbols and referenced publications; general; spatial resolution; scatter fraction, count losses and randoms measurement; sensitivity; accuracy: corrections for count losses and randoms; image quality, accuracy of attenuation and scatter corrections.