After the development of two major techniques - SPECT (Single Photon Emission Computed Tomography) and PET (Positron Emission Tomography) to image the human subjects in a three-dimensional direction in the 1980s, many radiotracers have been used for functional neuroimaging. Still it would be very important study to develop selective radiotracers for functional neuroimaging. New radiotracers will help to expand the knowledge of neurotransmitter systems and of the genetic contribution to receptor or transporter availability. Neurotransmitter depletion-restoration studies, the distribution of brain functions and their modulation by neurotransmitter system aid in better understanding and limiting the side effects of drugs used as well as newly developed. In audition, these radiotracers will be thus very useful to gain a better understanding in biochemical and pharmacological interactions in living human. This review mentions the introduction of radioligands for the functional neuroimaging. Although significant progress has been achieved in the development of new PET and SPECT ligands for in vivo imaging of those receptors and transporters, there are continuous needs of new diagnostic radioligands.