A two-dimensional, variable property, mathematical model of the transient pyrolysis of tobacco particle, in response to the smoldering (low heating rate) and puffing (fast heating rate) conditions in a burning cigarette, is presented. The model considers pyrolysis of tobacco obeying four-step Arrhenius kinetics, evaporation of water from tobacco following a mass-transfer and rate-determined process, and the formation of carbonaceous residue. From the physical point of view, the model describes convective, conductive and radiative heat transfer, and velocity and pressure variations interior to the porous tobacco particle (Darcy’s law). Furthermore, porosity, permeability and thermal conductivity vary with the composition of the reacting medium. Time and space evolution of the main variables, and reaction product distribution, are simulated by varying the tobacco heating rates.