Free formaldehyde emission from wood based panels is the result of polycondensation glues. We studied the impact of wood species on the leakage of free formaldehyde. We made three-layer particleboards from 4 wood species, and then through WKI method measured the emission of free formaldehyde. We used the following tree species: beech (Fagus sylvatica), oak (Quercus robur), spruce (Picea abies) and willow (Salix alba). As a test or control panel we used the panel prepared from industrial particles. The appropriate wood species reduce the amount of formaldehyde emitted; the reason being polyphenolic substances such as extracts, lignin and tannin. By mixing the different wood species in industrially prepared panels, low emission of formaldehyde and good mechanical and physical properties are achieved.