Our approach to coherence analysis of the on-going EEG yields data on the cooperation between all possible electrode sites of the 10/20 system. This procedure compares epochs during mental activity with epochs of EEG at rest and takes into account only significant differences which are represented as lines between the respective electrodes on maps of the brain surface. The patterns thus obtained reflect the temporal average of the changes of the overall coherence pattern caused by any mental task. They are interpreted as reflecting differential attention required for the achievement of the mental task in question. Acts of creative thinking, be it verbally, visually or musically, are characterized by more coherence increases between occipital and frontopolar electrode sites than any other mental tasks. The results are interpreted by a stronger involvement of long cortico-cortical fibre systems in creative tasks.