Background: To investigate the causes of paravalvular aortic regurgitation (PAR) after the implantation of the Medtronic CoreValve prosthesis (MCRS). Methods and Results: Fiftysix patients underwent MSCT before TAVI with a MCRS and PAR was assessed with transthoracic echocardiography (TTE) between 5 and 10 days after TAVI. The aortic annulus smallest and largest orthogonal diameters and the mean diameter from the area were determined on MSCT on an axial image at the nadir of all three native leaflets. PAR was related to relevant anatomical structures on MSCT according to a clockface in the orientation of the parasternal short axis view on TTE. PAR ≤ 1 was present in 25% of the patients and was associated with a larger annulus, a lower degree of over sizing and with more aortic root calcification. On MSCT post TAVI malapposition was seen predominantly at the aorto-mitral fibrous continuity and the aspect of the largest diameter of the aortic annulus on the inside curve of the ascending aorta. PAR was predominantly seen at these two anatomic locations and less frequent in the area that contains the ventricular membranous septum and the area between the non-and right coronary sinus. Conclusions: Mild to moderate PAR is common after TAVI with the MCRS. The availability of additional (larger) prosthesis sizes in combination with improved sizing based on mean annulus diameter (e.g., DCSA) may help to reduce PAR.