Previous studies have presented conflicting results regarding the predictive value of various clinical symptoms and signs for performing computed tomography (CT) scan in minor head injury. Moreover, despite the presence in the literature of several similar publications regarding whether or not CT should be employed at the time of presentation of minor head injured patients, data regarding delayed CT are limited. The objective of this study was to determine whether high-risk criteria represent a significant indication for initial CT scan in patients with minor head trauma, and whether or not analysis using delayed CT scan is necessary in patients with high-risk criteria before being discharged. Patients presenting to the Emergency Department with minor head trauma between September 1, 2003 and September 1, 2004 were evaluated prospectively. After being divided into two main groups, low- and high-risk, four separate sub-groups based on age were established. Initial spiral CT examination was done within 3 h of trauma on all patients in addition to a delayed control CT scan in those with high-risk criteria between 16 and 24 h after trauma. The difference between the high- and low-risk groups in terms of abnormal CT findings was statistically significant (p < 0.0005). Among high-risk patients there was a significant difference between patients with a Glasgow Coma Scale (GCS) score of 13 or 14 and those with a GCS score of 15 (p < 0.0005). The relationship between vomiting and abnormal CT scan was significant (odds ratio 4.61, 95% confidence interval 2.20-9.64, p = 0.0001), and the relationship between abnormal CT scan and suspected skull fracture was also significant (odds ratio 3.46, 95% confidence interval 1.52-7.91, p = 0.0032). No significant correlations between other high-risk criteria and abnormal CT scan were determined. The difference between initial and delayed CT scans in patients with high-risk criteria was not significant (p = 0.161). Low-risk patients with a GCS score of 15 may be discharged without initial CT scan being performed. Initial CT scan absolutely must be performed, however, on patients with GCS < or = 15 in the event of vomiting or suspected skull fracture, even if isolated. Even though the difference between initial and delayed CT scans in patients with high-risk criteria is not significant, it is our opinion that it is still prudent for delayed CT scan to be performed, particularly on patients whose GCS score does not rise to 15, or decreases.