The aim of this study is to show the connection between the morphometrical analysis of the width of the lateral ventricles measured in CT and MR images and the power of the frequency spectra of EEG signals in a total of 120 patients with epilepsy suffering from complex partial seizures without the clear localization and without the visible lesion. More than 800 CT and MR images of 120 patients with epilepsy were analyzed by the two-dimensional morphometrical analysis according to the methods presented in this study. Indices of the relation between the width of the right and left lateral ventricle were normally distributed. EEG frequency analysis of 8 channels, each of 32 seconds duration, was performed using 128 Hz sampling rate and FFT (Fast Fourie Transform) in 2 groups of patients consisting of 12 patients each: the first group with the significantly greater dimensions of the left lateral ventricle, and the second with the significantly greater size of the right one. Preliminary results of the analysis have shown that the absolute power of the theta frequency band was significantly increased in all brain regions in both groups of patients, and the relative ones in the parietocentral region bilaterally and in the left temporooccipital regions in patients with the wide lateral ventricle in the left hemisphere.