Our recent functional MRI and event-related potential studies suggest that neural mechanisms underlying identifications of environmental and personal risks are characterized by distinct neural structures and time courses. The current work further investigated the role of non-phase locked activity in dissociation of the neural processes of environmental and personal risks. We recorded electroencephalogram (EEG) from healthy adults when they identified risky and safe environmental or personal events depicted in words or phrases. Event-related synchronization (ERS) and desynchronization (ERD) in association with risky and safe environmental and personal events were calculated using Morlet's wavelet analysis. We found that, relative to the identification of safe environmental events, the identification of risky environmental events induced increased theta band power at 260-380 ms over the frontal cortex and increased alpha band power after 700 ms with a wide scalp distribution. Moreover, theta band powers associated with the identification of risky environmental events correlated positively with subjective ratings of the risk degree of environmental events. In contrast, the identification of risky personal events was linked to decreased alpha band power at 740-900 ms with a wide scalp distribution compared with the identification of safe personal events. Our findings indicate that theta and alpha band neural oscillations are involved in differentiation between environmental and personal risks.