Additive manufacturing is a set of processes that can produce parts of objects with relatively complicated geometry based on a 3D computer model, layer by layer. Prototypes, molds and high-precision tools, as well as functional parts for use, can be made successfully using additive processes. However, the speed of production, the choice of materials and the dimensions of the model are currently limited. Fused Filament Fabrication (FFF) is the most widely used type od additive manufacturing and is based on the process of extruding material through the head of a 3D printer. The print head melts the polymer, i.e. the filament, the melted filament is placed on the print plate and the object is fabricated layer by layer. The aim of this work was to produce a functional filament from cyclic olefin copolymer (COC) with the addition of TiO2 and CNT fillers, with a diameter of 1.75 mm and the possibility of ± 5% deviation. Titanium dioxide is characterized by photocatalytic properties, so it is used as a photocatalyst, while carbon nanotubes were used to improve the photocatalytic activity of TiO2. Using composites thus produced, it is possible to degrade pollutants in the water in the presence of sunlight or UV light. The fabricated filaments were used to print test tubes using a Zortrax M200 3D printer. Of the ten filaments prepared, only six filaments could be used to print test samples. The printed test samples were characterized by testing the mechanical properties on a UTM and by thermogravimetric analysis (TGA). When the mechanical properties of the samples were examined, it was found that the COC100 sample was the stiffest, while the COC-10T-0,1C sample was the least stiff. By thermogravimetric analysis of three samples with different filler content, it was found that the thermal decomposition of sample COC-15T-0,25C starts at the highest temperature, which means that it is also more thermally stable than the other samples.