Studies described in this paper were conducted in order to determine the dependence between the conditions of ligninocellulosic substrate pretreatment and its suceptibility to enzymic hydrolysis. In view of this, a semi-empirical mathematical model was used to examine the process of enzymic hydrolysis of cellulose by assuming that this reaction proceeds as a sum of two first order reactions with different rates of reactions. The application of quasi-Newtonian equations allowed for the determination of percentage fractions of easily and non-easily hydrolised cellulose in the structures of pretreated substrates.