In the paper, the results were presented of a research the objective of which was to determine the effect of sunflower oil addition (10, 20, 30, 40 %) and measuring (rated) voltage frequency (20 Hz – 2 MHz) on the electric conductivity changes in butter and fat mixes. The highest rate of changes in the conductance parameters (admittance, conductance, impedance, and resistance) of butter and fat mixes were found in the frequency range from 20 to 100 Hz. The values of those parameters varied in the range from ca. 5.5. to 107 % along with the increasing content of sunflower oil. The highest changes in the above named frequency range referred to the conductance and admittance. With the increasing content of oil in butter, the conductance values of fat mixes varied from ca. 7 to 107%, and the admittance values from ca. 5.5 to 40%. Also, statistically significant differences (α ≤ 0.01; α ≤ 0.05) were found between the admittance values of fat mixes with various contents of sunflower oil and of butter. On the basis of the results obtained, it was concluded that further analyses to determine the sunflower oil content in fat mixes and to detect adulteration thereof should be focused on the measurements of admittance and conductance.