Volatile and semi-volatile organic acids from cigarette smoke were converted to their methanoic esters. Qualitative analysis was by headspace solid-phase micro-extraction (SPME) and gas chromatography with scan mode mass spectrometry. Butanoic acid, hexanoic acid, 2-furancarboxylic acid, octanoic acid, nonanoic acid, benzoic acid, benzeneacetic acid, tetradecanoic acid, hexadecanoic acid were quantitated using derivatization headspace SPME and gas chromatography with selected ion monitoring mode mass spectrometry. Qualitative analysis of the smoke from 4 cigarette brands demonstrated the utility of this technology in cigarette smoke volatile and semi-volatile acids analysis. More than 60 organic acids were detected using this method. Quantitative and qualitative analyses of the headspace of derivatized cigarette smoke were processed using an 85-^µm polyacrylate SPME fiber.