The aim of this study was to examine the possibilities of additive technologies, fused filament fabrication and stereolithography for the purpose of manufacturing functional microreactors. Another main objective was to design a way of connecting microreactors with small diameter teflon tubes to allow input of reactants and output of products from microreactor. The basic requirements that the connection must meet are that it does not leak, it is reliable, easy to disassemble and assemble, and chemically inert. In order to investigate the influence of the microchannel dimension on the chemical reaction kinetics but also to demonstrate the functionality of the whole system, a biofuel synthesis was performed in the microreactor. For the determination of conversion at different retention times, a method for quantitative biofuel analysis by FTIR was developed. Commercially available transparent filaments of a variety of polymers can be used for producing microreactors by fused filament fabrication. Chemical compatibility of filaments in contact with reactants and reaction products is an important property to be investigated before using the material. Polypropylene based filaments were selected as the most suitable material and microreactors for the synthesis of biodiesel were made from it. Microreactors with quadratic cross-section of microchannels of different sizes were made and decrease of microchannel volumes were observed from predicted computer model. Stereolithography has shown greater resolution and it is possible to make much smaller details in relation to the fused filament fabrication. The main limitation of stereolithography for microreactor production is the inability to drain residual uncured resin from the microchannel. This method has successfully created a microreactor with 900 μm x 900 μm cross-sections and a length of only 3.5 cm. The microreactors with closed channel dimensions of 400 μm x 400 μm were successfully created by fused filament fabrication. The cross-sectional dimension of the microchannel affects the conversion of biodiesel at the retention time of τ = 0.5 min and a clear trend is visible; by decreasing the size of the microchannel, the conversion is increased, but at higher retention times this trend is lost and with at retention time of τ = 4 min, regardless of the microchannel dimensions and transverse cross-section, a similar conversion is achieved.