Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 6 4 2021 11 27 164 168 Reza Erfanian Otorhinolaryngology Research Center, Amir A’lam Hospital, North Sadi Ave, Tehran, Iran. Saeed Sohrabpour Otorhinolaryngology Research Center, Amir A’lam Hospital, North Sadi Ave, Tehran, Iran. Farrokh Heidari Otorhinolaryngology Research Center, Amir A’lam Hospital, North Sadi Ave, Tehran, Iran. Saeed Shakiba Otorhinolaryngology Research Center, Amir A’lam Hospital, North Sadi Ave, Tehran, Iran. 2020 10 04 2020 12 13 Vascular anomalies form a significant portion of congenital defects and venous malformations are the most prevalent type among adults. Multiple imaging modalities have been proposed for pre-operation assessments. Although some studies have reported Magnetic Resonance Imaging (MRI) as the most valuable modality, in many situations, CT scan remains the equipment of choice due to its availability. In each case, a precise assessment of the malformation is needed. In two cases mentioned in our study, prior to the operations, only a monophasic CT scan was performed that resulted in missing evidence of severity and extent of venous malformation. One of the imaging procedures is a three-phase CT scan. Although in the monophasic CT scans, a delay of 65 seconds is applied, in three-phase CT, both filling in and washing out are notable, which gives three-phase CT a more predictive value about flow pattern over monophasic CT. https://crcp.tums.ac.ir/index.php/crcp/article/view/409