As the serotonin transporter (SERT) is involved in several neurodegenerative and psychiatric disorders, radiopharmaceuticals to image the SERT by PET or SPECT would be very valuable in studying these diseases. For the development of imaging agents, we have synthesized novel derivatives of recently reported diphenylsulfide SERT ligands, in which the sulfur atom linking the two phenyl rings was replaced by an oxygen, sulfinyl, sulfonyl, ...