Žitniak, A. 2020: MDF board surfaces evaluated in terms of their surface finish with foils and colour stability of these foils in accelerated ageing process. Diploma Thesis. Zvolen: The Faculty of Wood Sciences and Technology. Technical University in Zvolen, 2020. 88 pp. Diploma thesis supervisor: prof. Ing. Jozef Kúdela, CSc..The diploma thesis has been focused on the study and analysis of specified surface properties of medium-density fibreboards (MDF). The primary purpose was to acquire data relevant for the surface treatment of these materials. The second part of the thesis presents the results of monitoring the colour stability of MDF surfaces subject to accelerated ageing process simulating interior conditions. The monitored MDF boards were finished with commercially produced paint coatings and foils. The study results on the morphology of the MDF surface show structural differences between the MDF surfaces and the middle layers. The surface layer, thick from 1.5 to 2 mm, consisted of fine wood fibres and wood dust -impregnated with the adhesive and paraffin. In the inspected MDF boards, this surface layer, in interaction with the pressing technology, induced lower roughness and clearly higher resistance against water and against non-polar liquids, The MDF surfaces also exhibited low surface free energy with dominating dispersion component. IN the case of applying film-forming substances, this may result in uneven spreading of these substances across and their poorer adhesion to the MDF surface. Evaluation of the MDF-finished surface discolouration associated with accelerated ageing, simulating interior conditions, revealed that in all cases, the lightness value L* maintained unchanged during the whole period of the ageing process. The values of the colour coordinate a* varied only to a minimum extent. The major changes were observed in the case of the coordinate b*, which was reflected in the overall colour difference ΔE. All the surface finishes kept their original gloss values throughout the whole ageing process. In summary, it may be stated that six out of the eleven studied surface finishes were found well resistant against photo-degradation. As such, they may be supposed to preserve their visual appearance for long time.