In the last decade many authors have found evidence on the influence of smoke from fires on the cloud-to-ground (CG) lightning characteristics, both in the lifetime scale of individual storms and on a climatological scale. In general, the observations indicate that the peak current and percentage of positive flashes increase in thunderstorms injected with smoke, while the negative peak current decreases. This article investigates the validity of these findings in thunderstorms injected with large concentrations of smoke from fires in the Amazon region, comparing CG lightning characteristics in the dry (polluted) and wet (clean) seasons, as well as using a new methodology, based on results of a numerical simulation model of atmospheric transport of tracers coupled to a biomass burning emission model. The results confirm the previous findings and, in addition, give a first estimation of the sensitivity of these parameters to changes in the smoke concentration.