ATR-FTIR spectroscopy and conventional analysis techniques were performed to characterize the chemical structure of different coniferous (cedar, fir, Calabrian pine, and spruce) and deciduous (chestnut, oak, alder, and beech) tree barks. The cell wall components (holocellulose and lignin) and extractives of tree barks were determined using conventional analysis methods. Chemical analysis indicated that the polysaccharide contents of tree barks were very low compared to lignin and extractives content. Substantial dissolution of tree barks was brought about by 1% NaOH. FTIR analysis method is an easy and reliable way to determine the functional groups of tree bark components. The levels of carbohydrates and lignin, as determined by ATR-FTIR spectral analysis, were consistent with the results of conventional analysis. The highest content of lignin was in the alder species for the deciduous trees and in the cedar type for the coniferous trees.