Varying lignin and cellulose contents in agro-waste cause feedstock to respond differently during their thermochemical conversion. The effect of pyrolysis temperature (400, 500, 600 degrees C) and feedstock composition on product yields and gas composition of olive kernel and corncobs was investigated in a lab-scale, fixed-bed reactor under a 20 mL/min of nitrogen flow at atmospheric pressure. Results were compared to those obtained in the same pyrolysis setup from model synthetic mixtures of cellulose and lignin, in an attempt to simulate the composition of real feedstocks. Experimental results showed how lignin and cellulose influence the thermochemical process and how non-negligible synergistic effects among lignin and cellulose are affecting the thermochemical process outcomes. Lignin affects the increase of char yields obtained from the synthetic mixtures more than it does in real feedstock. Similarly higher yield of CO2 in produced gas is reported from pyrolysis of synthetic mixtures compared to that obtained from real feedstock containing the same amount of lignin. Thus, the pyrolysis behavior of raw feedstock cannot be satisfactorily predicted by the behavior of their main components in an "additive" rule, as interactions are also taking place between organic components, as well as ash inorganic elements and organic matter which promote more complex synergistic effects of the components of the lignocellulosic matrix.