Abstract Background Transcatheter interventions are currently undertaken using “generic” fluoroscopic viewing angles. However, the position and orientation of heart structures may vary across patients and disease-specific remodeling processes. Objective This study uses multislice computed tomography to determine optimal fluoroscopic viewing angles of the aortic and mitral annuli, the left atrial appendage and the atrial septum. We explored differences between patients with severe aortic stenosis (AS) and severe mitral regurgitation (MR). Methods and results The multislice computed tomographies of 28 patients with severe aortic stenosis (AS) and 32 patients with severe functional mitral regurgitation (MR) were analyzed. For each patient, we evaluated the optimal fluoroscopic viewing angles of the aortic and mitral annuli ( en face , maximal and minimal diameters, aortic root with right, left and non coronary sinus in center), left atrial appendage orifice ( en face , maximal and minimal diameters), and atrial septum (fossa ovalis) en face. The TAVR implantation view with right coronary sinus in center was LAO 9 – CRA 0 in the AS group and LAO 6 – CAU 5 in the MR group (p = NS). AS and MR patients differed significantly with respect to the fluoroscopic angulation of the aortic annulus en face (8.3°), the aortic annulus maximal (17.7°) and minimal (18.5°) diameters, the mitral annulus aorto-mural diameter (11.3°), and the left atrial appendage orifice en face (11.1°) (all p-values<0.05). Conclusion Optimal fluoroscopic viewing angles of left-sided structures vary considerably between patients. Multislice computed tomography is a valuable tool to determine the most procedurally relevant angulations, with the potential to optimize procedural safety, efficacy and duration.