An assessment of the SO 2 adsorption capacity of a series of chars obtained by N 2 pyrolysis at different temperatures from a low-rank coal with high ash content was conducted. The adsorption process was carried out at representative flue gas conditions. Chars obtained by nitrogen pyrolysis at 500, 600, 700, 800 and 900°C were characterized by the following techniques: XRD, atmospheric absorption spectroscopy, Fourier-transform IR spectrometry, Hg porosimetry, N 2 and CO 2 surface areas, and acid-base titration. Correlations between the performance of these chars and their physicochemical features were investigated. The SO 2 adsorption capacity of pyrolysed chars depends mainly on their surface area, but the content and type of functional groups and their accessibility are also important parameters to be considered.