The PET radiopharmaceuticals are prepared on the spot in most cases due to the short lifetime of the isotopes used. The first step of this process is the isotope production by small cyclotrons. The synthons made from the isotopes react with the precursor of the given radiopharmaceutical. The target compound selected from the reaction mixture is ready for injection after purification, formulation and sterile filtration. In addition to [18F]-FDG, [11C]-methionine and [15O]-butanol routinely used for diagnostic purposes in the PET Centre of the University of Debrecen, a number of other radiopharmaceuticals are synthesized for use in research from time to time.