Our aim was to find chemical structure of particleboards using FT-IR spectroscopy. Analysis based on shining through samples with light wave frequency from 400 cm-1 to 4000 cm-1 by measuring transparency or quantity of absorbed light, depending on the wave length. Spectra were measured using DRIFT (Diffuse Reflectance Infrared Fourier Transform) technique, which is most frequent for dust analysis (in our example ground particle). We used particleboards from Russia, Italy and Slovenia. One particleboard sample was glued together with melamine-formaldehyde, others with urea-formaldehyde glue. In receiving spectra from 400 cm-1 to 4000 cm-1, we concentrated on wave range from 650 cm-1 to 1750 cm-1. In that range, functional group cellulose, hemi-cellulose and lignin in wood occur. Using FT-IR spectroscopy we determined chemical structure in particleboards or functional group cellulose, hemi-cellulose and lignin. It was found out that by comparing FT-IR spectra of particleboards the ratio of cellulose, hemi-cellulose and lignin is changed, influenced by different use of glue (MF, UF), process of making particleboards, tree species and ionizing radiation.