It is well known that an aqueous extract of cigarette smoke generates reactive oxygen species. The method of analyzing hydrogen peroxide in smoke extract has been reported at TSRC 2008, and a mechanism for the generation of those species has been proposed at TSRC 2009. These studies suggested that the hydrogen peroxide accumulated in the extract is an important precursor for the generation of hydroxyl radicals. To elucidate the origin of hydrogen peroxide in cigarette smoke, the particulate phase of the smoke was extracted and the extract was fractionated with reverse-phase HPLC under acidic conditions. After the pH of the fractions was adjusted to basic values, hydrogen peroxide was detected not only in the fractions containing hydroquinone and catechol but also in fractions containing other components. These components were eluted using longer retention times than those applied for hydroquinone and catechol. The concentration of phenolic compounds in the fractions was evaluated by a colorimetric test. The absorbante at 750nm in the test and the yield of hydrogen peroxide showed a positive correlation. These results support the idea that phenolic components are possible precursors of hydrogen peroxide; precursors other than hydroquinone and catechol would be more hydrophobic than the two components.