A technique for performing simultaneous PET emission and transmission scans is validated in a fluoro-deoxyglucose study. A point source masked into a fan beam of annihilation photons orbits the patient section under study. Coincident events are sorted into two buffers, or rejected, based on the source's position. Both static and dynamic frames of independent and simultaneous studies are compared. The noise effective count rate is reduced to 62% of the value during normal studies. However, the increase in the coefficient of variation in cortical regions is less than 6%. The RMS difference between profile contours through many brain regions is approximately 40% higher comparing two simultaneous emission/transmission scans than when the same analysis is performed on independent emission scans. This difference appears to be due to the noise patterns arising from the use of different transmission scans.