The objective of the study was to investigate and compare the brain cortical activity, as indexed by quantitative electroencephalographic (qEEG) power, coherence and asymmetry measures, in panic disorder (PD) patients during an induced panic attack with a 35% CO(2) challenge test and also in a resting condition. Fifteen subjects with PD were randomly assigned to both 35% CO(2) mixture and atmospheric compressed air, in a double-blind study design, with EEG being recorded for a 20-min period. During induced panic attacks we found a reduced right-sided frontal orbital asymmetry in the beta band, a decreased occipital frontal intra-hemispheric coherence in the delta band at both right and left sides, a left-sided occipital delta inter-hemispheric asymmetry and an increased relative power in the beta wave at T4. Our data showed a disturbed frontal cortical processing, pointing to an imbalance of the frontal and occipital sites, common to both hemispheres, and an increased right posterior activity related to the high arousing panic attack condition. Those findings corroborate the Neuroanatomical hypothesis of PD.