The study presented in this paper is based on the results of a field experiment conducted in the years 2014-2016 at the Research Station for Cultivar Testing COBORU at Uhnin (51°34', 23°02'E), on a slightly acidic grey-brown podzolic soil. The experiment was performed with the random sub-block method, in a split-plot related system, in three replicates. The first-order experimental factor were potato cultivars (Vineta and Satina), and the second-order factor were six variants of potato plant protection: A – with the use of fungicides against potato blight, variants B, C, D, E – with the application of effective microorganisms, and variant F – without the application of fungicides and effective microorganisms, as the control treatment. Organic and mineral fertilisation for potato cultivation was at a constant level (20 t ha–1 white mustard for ploughing-over and 90 kg N, 39.3 kg P, 112.0 kg K ha–1). The experiment was conducted in conformance of the methodology of estimation of economic value of crop plants cultivars in force at COBORU (Research Centre For Cultivar Testing) stations. The scope of the study comprised the estimation of the effect of application of fungicides, EM (Effective Microorganisms) and herbal extracts on the yield and on the quality parameters of seed potatoes. The protection variant with the use of fungicides contributed significantly to a decrease in the yield of seed potatoes, relative to the control treatment. All plant protection variants caused a significant increase in the numbers and multiplication factor of seed potatoes, relative to the control treatment. The genetic traits of the cultivars had a significant impact on the yield and number of seed potatoes, but they did not differentiate the average mass of seed potatoes and the values of the multiplication factor. The weather and soil conditions in the years of the study significantly determined the evaluated parameters.