The paper describes the fast pyrolysis conversion of lignocellulosic materials inside a bubbling fluidized bed. The impact of biopolymers distribution in the biomass feed, namely hemicelluloses, cellulose, and lignin, on the yields and properties of pyrolytic bio-oils and chars was investigated. Although it is not possible to deconvoluate chemical phenomena from transfer phenomena using bubbling fluidized bed reactors, the key role of hemicelluloses in biomass feedstocks was illustrated by (i) its influence on the production of pyrolytic water, (ii) its impact on the production of organics, apparently due to its bonding relationship with the lignin and (iii) its ability to inhibit the development of chars porosity, while the cellulose appeared to be the precursor for the microporous character of the biochars. These results are of interest in the selection of suitable feedstocks aimed at producing bio-oil and char as fuels and soil amendment, respectively.