The knowledge of the uncertainty associated to an analytical method is necessary to evaluate the quality of the results measured by itself. In this work the uncertainty associated to analytical measurement of polycyclic aromatic compounds (PAHs) in ambient air by thermal desorption coupled with gas chromatography-mass spectrometry (TD-GC/MS) was evaluated. The study was focused on analyses of particulate phase (PM10) and the results were compared to those obtained a conventional solvent extraction (Soxhlet-GC/MS). The main sources for combined uncertainty were calibration curve, recovery of the extraction stage, area or volume of sample and volume of air. The TD-GC/MS reported lower combined uncertainty (< 10%) than Soxhlet-GC/MS (values between 11 and 18%) for measurement of particle-bound PAHs in air. The major uncertainty contributions resulted from the recovery of each analyzed PAH and the calibration curves.