The characterization of char obtained from the vacuum pyrolysis (8 KPaabs, 460 degrees C, 18 degrees C/min) of sugar cane bagasse followed by steam gasification (60 wt % of steam, 700-900 degrees C) was studied. The influence of different chemical pretreatments prior to pyrolysis (acetone, ethanol, HNO3 and HF) on the ash content, the pore structure, and chemical composition of resulting chars and activated carbons were investigated. Changes in the pore structure were observed during the pyrolysis process and the steam gasification, namely, the development of a channel network and the increase of meso- and macroporosity distributions, respectively. These porous changes affect the pyrolytic yields. Clear influences of the surface area and ash content on the pyrolytic water yields and the inorganic devolatilization effect on the meso- and macropore distributions of chars were shown. Furthermore, the structural reorganization of chars obtained during the vacuum pyrolysis of HF and solvent-leached bagasse was beneficial to their reactivity toward steam gasification.