This study sought to introduce a computed tomography (CT) protocol for optimal planning of vein of Marshall (VOM) catheterization. Ethanol infusion into the VOM (Et-VOM) is increasingly used in atrial fibrillation ablation. Preprocedural CT was performed with either a conventional (conv-CT; n=132) or an optimized CT protocol (VOM-CT; n=126) designed for obtaining on a single image both left atrial and coronary sinus (CS) enhancement. The detection rate and anatomical features of the CT-derived VOM were analyzed and the utility of VOM-CT protocol was assessed by comparing the procedural data. VOM was detected in 35% in conv-CT versus 63% in VOM-CT (P< 0.001). The VOM-CT protocol did not impair the assessment of left atrial anatomy and appendage patency. In VOM-CT, the detection of the VOM was related to body mass index and width of epicardial space on posterior wall. Mean distance between CS ostium and VOM was 36±7mm. Mean VOM diameter was 1.6 ± 0.3mm. On the CS circumference, the VOM emerged superiorly in 68% and postero-superiorly in 32%. Ethanol infusion into the VOM was attempted in 165 patients (77 conv-CT, 70 VOM-CT, and 18 without-CT). After registration in CARTO, the VOM segmented on CT matched its location on venography in all cases. As compared with conv-CT and without-CT, procedures guided by VOM-CT showed significantly shorter radiation time, shorter procedure time, lower amount of the contrast medium, and fewer contrast injections to obtain VOM catheterization. The proposed CT protocol allows for improved visualization of the VOM, translating into easier VOM catheterization.