Functional hemispheric asymmetry of the brain, despite the simplistic model well-known from popular literature, is relative rather than absolute. Hemispheres are not specialised to execute distinct cognitive functions (for example linguistic vs spatial). They differ rather in their ability and efficiency to perform definite cognitive processes. The aim of this paper is to reveal the relative nature of the division of competence between the two hemispheres, basing on the processing of complex visual patterns. The results of most studies indicate a right hemisphere superiority in processing a global shape and a left hemisphere superiority in processing local details. This relative hemispheric specialisation is clearly demonstrated by behavioral deficits due to unilateral lesions in neurological patients. These findings are consistent with the results of visual-field studies in normal subjects. Neuroimaging and electrophysiological investigations provide additional confirmation that the hemispheres are differentially specialized for global and local processing. Theories that attempt to explain the partwhole processing problem, usually posit that the two hemispheres differ in their sensitivity to spatial frequency information contained in complex visual patterns. They assume right hemisphere superiority in processing low frequencies information and left hemisphere predominance in processing of high frequencies information.