This research is dedicated to one of the most important problems of the special psychology diagnosis, differentiation of the children with minimal brain dysfunction. The with minimal brain dysfunction at the pre-school students institutionalized in orphanages has been studied. Through the angle of diagnosis and differentiation of children different forms of minimal brain dysfunction, the development particularities characteristic for some kinds of minimal brain dysfunction. Due to the implementation of one complex models of diagnosis, the form of minimal brain dysfunction of deprivation nature has been differentiated, manifested by great evident changes in the affective sphere development. The development particularities determined at different forms of minimal brain dysfunction allow establishing the diagnosis criteria of the cerebrogenic, somatogenic, psychogenic and deprivation forms.