In order to examine the independent and combined effects of depressive symptoms and traumatic brain injury on event-related potential (ERP) components, we classified traumatic brain injury (TBI) patients as depressed and non-depressed mood according to their scores on the Zung Self-rating Depression Scale (SDS). Non-depressed mood post-traumatic brain injury patients (NondepTBI, n=9), depressed mood post-traumatic brain injury patients (DepTBI, n=26), and normal healthy control subjects (HC, n=10) were assessed for N100, N200, and P300 latencies and amplitudes by the auditory "oddball paradigm". DepTBI subjects had significantly prolonged N200 latency and low P300 amplitude compared with the NondepTBI and HC groups. A longer P300 latency in the NondepTBI and DepTBI than in the HC groups was found. A prolongation of N200 latency accompanied by low P300 amplitude may be a characteristic of post-traumatic brain injury patients with depressed mood. Prolonged P300 latency may be more closely associated with TBI than with depression, as it was significantly greater in both the DepTBI and NondepTBI, than in the HC group.