Cortical activity in the human electroencephalogram alpha band was measured (by means of an event-related approach) in a pre- and a post-test (with intermediate training) while participants (n = 30) were confronted with divergent thinking tasks. Half of the participants received a divergent thinking training (over a time period of 2 weeks) which was composed of exercises structurally similar to those used in the pre- and post-test. Analyses revealed that the training group displayed higher task-related synchronization of frontal alpha activity (i.e. increases in alpha power from the pre-stimulus reference to the activation interval) than the control group. These findings are in line with the view of frontal alpha synchronization as a selective top-down inhibition process that prevents internal or top-down information processing being disturbed by incoming external input.