Prato cheese is a washed curd and semi-hard cheese produced from pasteurized cows' milk acidified by a mesophilic starter containing citrate-positive bacteria, and matured for a minimum period of 25 d. Volatiles play an important role in flavor perception of cheese and they are result of compounds formed by glycolysis, citrate metabolism, proteolysis and lipolysis. The aim of this work was to evaluate the formation of volatile compounds in Prato cheese after 30 d of refrigerated storage at 12°C. The compounds were determined by gas chromatography-solid phase micro extraction coupled to a mass spectrometer detector (GC-SPME-MS). Two grams of a mixture of cheese sample and sodium phosphate saline solution (1:3, w/v) were incubated in a sealed 20 mL vial for 15 min at 40°C and after that, the DVB/CAR/PDMS fiber was exposed to the headspace for 30 min. The fiber was desorbed in the injector (splitless mode) at 250°C for 1 min. Compounds were separated in a RTX-Wax (30 m × 0.25 mm × 0.20 μm, Restek). Electron ionization source was set at 70 eV and 250°C. MS data were acquired in SCAN mode (m/z 35–350). Identification was carried out by comparison with mass spectra of authentic standards or Wiley 9 library and Kovats retention index. Volatile compounds found were organic acids (C_4:0 to C_10:0), esters (ethyl butyrate, ethyl hexanoate), ketone (2-pentanone, 2-heptanone, 2-undecanone), alcohols (ethanol, 1-pentanol, 1-butanol, 1-hexanol, 3-methyl-1-butanol, 1-heptanol, 1-octanol) and aldehydes (hexanal, heptanal, nonanal, decanal, benzaldehyde) as a result of cheese glycolysis, lipolysis and proteolysis. From the citrate metabolism, we found acetoin, 2,3-butanediol, 2-butanone and diacetyl, which is associated with characteristic butter flavor of Prato cheese.