A facile method to determine the distribution of methyl groups in regioselectively methylated celluloses on anhydroglucose unit was developed using solution H-1-NMR analysis. The determination was deduced from the assignment of the signals of each proton, which directly attached to the glucopyranose ring carbon for partially methylated 2,3-di-O-methylcellulose samples observed in D2O. These data for the distribution of the methyl groups corresponded to those based on the gas-chromatographic analysis. This method using the H-1-NMR spectroscopy can facilitate the measurements of the distribution of methyl groups for randomly substituted and commercially available O-methylcelluloses.