Chemical pretreatment of softwood chips with kraft mill green liquor results in the selective retention of various chemicals in the chips. It was found that each chemical component in the green liquor exhibits a different physicochemical behavior in the wood. For example, sulfide was determined to exist in wood chips in three distinct forms: free (in the bulk), adsorbed (physically entrained in the solid matrix), and chemically bonded (that cannot be leached). The ratios among these forms are a function of the pretreatment conditions employed. For example, high temperatures and high sulfide concentrations increase the amounts of both the adsorbed and chemically bonded forms. Meanwhile, surfactants, anthraquinone (AQ, a pulping catalyst), and polysulfide (PS, an active pulping chemical) added to a green liquor pretreatment scheme augment the levels of the chemically bonded form. This investigation into the influence of the pretreatment conditions on sulfide behavior demonstrated that lignin dissolution is increased as the levels of sulfide in the wood chips are increased. In fact, of the three forms of sulfide available for wood chip interactions, the free sulfide form exhibited a negative influence on lignin removal during pretreatment, whereas the adsorbed and chemically bonded forms correlated directly with higher lignin dissolution.