It is difficult to study the genetic basis of psychological function/dysfunction due to its etiological complexity. Instead, we studied a biological marker, EEG power, which is associated with various psychological phenotypes and is closer to gene function. Previous studies have consistently demonstrated high heritability of EEG band power, but less is known about how common or specific genes influence each power band. For 519 adolescent twin pairs, spectral powers were calculated for delta, theta, alpha, and beta bands at bilateral occipital and frontal sites. All four bands were entered into a multivariate genetic model, with occipital and frontal sites modelled separately. Variance was decomposed into additive (A) and dominant (D) genetic factors, and common (C) and unique (E) environmental factors. Band heritabilities were higher at occipital (0.75-0.86) than frontal sites (0.46-0.80). Both common and specific genetic factors influenced the bands, with common genetic and specific genetic factors having more influence in the occipital and frontal regions, respectively. Non-additive genetic effects on beta power and a common environment effect on delta, theta, and alpha powers were observed in the frontal region.