Vaporization of bound water associated with cellulose fibres of natural (cellulose I) and regenerated cellulose (cellulose II) was investigated by differential scanning calorimetry in both dynamic and static conditions. Factors which affect water vaporization, such as sample handling, water content, heating rate, gas flow rate and temperature of holding were examined. It was found that vaporization peak is split: into two peaks, one is at around 60 degrees C and the other is at around 120 degrees C, when the samples were measured by slow heating rate (<2.5 degrees C min(-1)) and Low gas flow rate (<30 ml min(-1)). The high temperature vaporization peak is related with the structural change of amorphous chains of cellulose by desorption of bound water.