The curing kinetics of lignin-phenol-formaldehyde (LPF) and phenol-formaldehyde (PF) resol resins was studied by non-isothermal differential scanning calorimetry (DSC) at different heating rates. The data were fitted by means of the Borchardt-Daniels, Ozawa and Kissinger methods, which allow determining the kinetic parameters of both resins. The kinetic study has been realized to evaluate the effect of methylolated ammonium lignin sulfonate in the curing process of the lignin-phenolic resins. The results showed a slightly higher activation energy for LPF resin. It is attributed to the presence of modified lignosulfonate in this case. The obtained data, similar in both resins, indicate that the phenol can be replaced partially by a modified lignosulfonate in the phenolic resins. (C) 2004 Elsevier B.V. All rights reserved.