Abstract: In a method of manufacturing bonded products, comprised completely or partially of cellulose or a cellulose derivative, such as saw dust, wood chips, paper or vegetable fibres, a condensation resin between an aldehyde, preferably formaldehyde, and urea, melamine or a phenol type is used as an adhesive. The product is irradiated to at most 5 Mrad with ionising radiation. Then the material will undergo a certain cross-linking. Residual quantities of uncured adhesive substances are reduced at the same time. The radiation dose is adjusted so that residual quantities of aldehyde in the material will be reduced. Preferably, also the residual quantity of formaldehyde in the material is reduced. By adding additives containing olefinic, acrylic or comparable groups the extent to which cross-linking takes place is increased.