Samples Alamo, Kanlow, GA993, and GA992 switchgrass, Panicum virgatum L., were partitioned into two morphological portions, leaves and internodes, and analyzed for chemical compositions in the previous study. These samples underwent a hydrothermal pretreatment, followed by cellulase and cellobiase treatment. Hydrothermal pretreatment was found to provide comparable gravimetric yields ranging from 48.1 to 51.4%. However, cellulose digestibility of the pretreated leaf portion of the switchgrass exhibited 32.5% greater glucose yield (77.4%) than that of the internode portion (44.9%). The carbohydrate profiles, cellulose crystal structure, and degree of polymerization (DP) of the cellulose were analyzed for native and pretreated leaves and internodes. The results demonstrated that pretreated leaves and internodes had similar chemical constituent profiles and chemical structure for cellulose and lignin but significant differences for the DP of a-cellulose. The lower DP of cellulose for the pretreated leaf portion of the switchgrass was attributed to be a factor for the enhanced cellulose digestibility in comparison with the intemode portion.