We investigated the reactivity of O( 1D) towards two types of hydrogen atoms in CH 3OH. The reaction was initiated on irradiation of a flowing mixture of O 3 and CD 3OH or CH 3OD at 248 nm. Relative vibration-rotational populations of OH and OD (1 ≤ v ≤ 4) states were determined from their infrared emission recorded with a step-scan time-resolved Fourier-transform spectrometer. In O( 1D) CD 3OH, the rotational distribution of OD is nearly Boltzmann, whereas that of OH is bimodal; the product ratio OHOD is 1.56 ± 0.36. In O( 1D) CH 3OD, the rotational distribution of OH is nearly Boltzmann, whereas that of OD is bimodal; the product ratio OHOD is 0.59 ± 0.14. Quantum-chemical calculations of the potential energy and microcanonical rate coefficients of various channels indicate that the abstraction channels are unimportant and O( 1D) inserts into the C-H and O-H bonds of CH 3OH to form HOCH 2OH and CH 3OOH, respectively. The observed three channels of OH are consistent with those produced via decomposition of the newly formed OH or the original OH moiety in HOCH 2OH or decomposition of CH 3OOH. The former decomposition channel of HOCH 2OH produces vibrationally more excited OH because of incomplete intramolecular vibrational relaxation, and decomposition of CH 3COOH produces OH with greater rotational excitation, likely due to a large torque angle during dissociation. The predicted OHOD ratios are 1.31 and 0.61 for O( 1D) CD 3OH and CH 3OD, respectively, at collision energy of 26 kJ mol -1, in satisfactory agreement with the experimental results. These predicted product ratios vary weakly with collision energy.