The objective of the paper was to determine appropriate relations between efficiency and effectiveness of implementing the scientific and technical progress and work organization with the use of the EU funds. In 2004-2009 70 selected family farms from the province of Biłgoraj, which benefit from the EU funding for technical modernization, were investigated. The period prior to and after obtaining the aid was analysed. Efficiency of using agricultural engineering referred to the amount of aid and the net commodity production was the highest in farms, which were big with respect to the area and economy. The costs of obtaining grain units (GU) were decreasing along with the increase of the economic size of farms, while the net commodity production was rising in these farms. Efficiency of using the EU funds for technical modernization was presented in each investigated group of farms, but these funds were the most effectively used in farms with the area up to 70 ha of AL, which is mainly determined by the AL area, economic size, level of the obtained farming effects and the level of providing the work station with infrastructure. In farms with smaller areas, a high level of the employment infrastructure, at the simultaneous loading with high costs of mechanization means, was proved. Modernization of farms, considerably influences the production process, all mechanization rates increase including: the replacement value of mechanization means, the level of technical infrastructure of employment, installed power, objectified work inputs, human labour expenditures, employee infrastructure, energy infrastructure of employment, mechanization degree and the net commodity production (GU∙ha^-1 AL).