About 20% of the total wood carbohydrates removed from softwood chips from a pretreatment with a high-sulfidity, carbonate-rich solution known as green liquor (GL) are mainly derived from glucose and mannose. The salient chemical events occurring during GL pretreatment are sugar readsorption in a neutral or slightly alkaline environment and substantial mannan dissolution. However, it appears that pentose saccharides are more easily adsorbed onto fibers than hexose saccharides. Mannose, for example, undergoes degradation easily, with no obvious readsorption during the entire process. A higher GL concentration can enhance both tendencies of reabsorption and degradation. A striking finding is that, during the pretreatment phase, hydrogen sulfide appears to react with wood composites to form a very tight bond that appears to be chemical in nature. The apparent chemical bonding behavior of sulfur in wood correlates with carbohydrates retention: a higher level of bonded sulfur results in higher carbohydrates retention. Finally, various additives applied during GL pretreatment were found to exert a significant influence on sugar retention.