Recently, the number of clinical PET centers is increasing all over Japan. For this reason, the monitoring and control of radiation exposure of employees, especially nurses, in PET-dedicated clinics and institutions are becoming very important issues for their health. We measured the radiation exposure doses of the nurses working at Nisidai Diagnostic Imaging Center, and analyzed the exposure data obtained from them. The exposure doses of the nurses were found to be 4.8 to 7.1 mSv between April 2003 and March 2004. We found that the nurses were mostly exposed to radiation when they had to have contact with patients received an FDG injection or they had trouble with the FDG automatic injection system. To keep radiation exposure of nurses to a minimum we reconfirmed that a proper application of the three principles of protection against radiation exposure was vital.