Patients with post-traumatic stress disorder (PTSD) suffer from a failure of cognitive control over emotional distracters. The physiological substrates of cognitive-emotional interactions and their breakdown in disease are, however, unknown. Here, we studied brain activity in PTSD patients and healthy controls in response to emotion-provoking pictures using electroencephalography and functional magnetic resonance imaging (fMRI). We demonstrate that in healthy individuals, emotion-induced frontal theta rhythm modulates activity in the beta rhythm mainly in sensory-motor regions. In contrast, in PTSD patients, beta activity is elevated irrespective of emotion, and is not modulated by frontal theta activity in response to negative emotion. EEG source localization and fMRI findings suggest that theta activity is localized to the prefrontal and anterior cingulate cortices while beta activity is localized to sensory-motor regions. We further found that beta activity in sensory-motor regions is related to the emotion-induced slowing of the motor response in healthy controls while the excess frontal theta activity in PTSD is related to the intensity of negative emotional experience. These findings reveal for the first time the importance of brain electrical oscillations and coherence in emotional top-down modulation and point to specific failure of these mechanisms in PTSD. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc.