Enzymatic hydrolysis of a large number of not-treated and pretreated plant materials of various origins containing different amounts of cellulose, hemicelluloses and lignin has been studied. To disclose the effect of chemical composition and structural characteristics on yield of glucose, a correlation analysis was performed and squared correlation coefficients (R2)were calculated. This analysis showed that hemicelluloses have a negligible impact on enzymatic digestion of the cellulosic component. Content of lignin affected negatively on enzymatic cleavage of cellulose, and namely an inversely proportional regression between content of lignin in the samples and yield of glucose was observed (R2 = 0.67). Conversely, increased cellulose content in the biomass affects positively on enzymatic digestion and glucose output (R2 = 0.84). To improve the correlation, an effect of crystallinity degree of cellulose on hydrolysability should be taken into consideration.As a result, the best correlationwithmaximumsquared coefficient (R2 = 0.98)was found for the dependence of glucose yield (Y) on the combined parameter Z, which includes the content and crystallinity of cellulose, as well as the content of lignin in the investigated biomass samples. As follows fromthe regression equationY=f(Z), an increase the content of cellulose, reducing of its crystallinity and decreasing of the lignin content in the samples promotes enzymatic cleavage of the cellulosic component.The discovered correlationY=f(Z) permits prediction the saccharification degree of pretreated biomass and can be used for choice the best pretreatment method. In particular, the nitric acid/alkaline pretreatment of herbaceous plants provides obtaining the delignified biomass enriched with low-crystalline cellulose that shows an excellent enzymatic digestibility.