Membrane introduction mass spectrometry (MIMS) coupled to a miniature mass spectrometer equipped with a cylindrical ion trap (CIT) analyzer was used to monitor the flavor components, 3-phenyl-2-propenal and methyl salicylate, found in cinnamon and wintergreen candies, respectively, directly from human breath. The poly(dimethylsiloxane) (PDMS) membrane was operated in a trap-and-release mode, where the temperature of the membrane was cycled during the experiments, which permitted temporal resolution of the two compounds of interest, facilitating their observation in the complex sample. Under these thermally driven conditions, the 10–90% rise times for both compounds are similar (15 s for methyl salicylate, 17 s for 3-phenyl-2-propenal), but the difference in diffusivity means that the signal for 3-phenyl-2-propenal is delayed and the 10% point occurs 6 s later than that for wintergreen. Additional specificity needed for complex samples was gained by using tandem mass spectrometry. Copyright © 2002 John Wiley & Sons, Ltd.