The aim of this study is to testify the effects of different inhomogeneious tissues on computed electrical potential fields associated with the electroencephalograph. The inhomogeneity of head tissues is included in head model using so-called pseudo conductivity created by limited, experimental measured data. Simulations were performed varying the conductivities assigned to the different head compartments in the model. Comparisons of different conductivity combinations followed one of two basic schemes: 1) a piecewise homogeneous multi-layer head serves as the reference against which we compared simulations with a single tissue assigned its pseudo conductivity, and 2) a fully inhomogeneious head serves as the reference and we remove the effect of individual tissue by assign it the homogeneous conductivity value. The result both in 1) and 2) show that the skull have larger impacts on the head potential distribution than other element. It also show that the size of the effect is not neglectable in all tissue. This study suggest that accurate representation of tissue inhomogeneity has a significant effect on the accuracy of the forward solution.