This paper presents a numerical study on the effect of the relative geometry between piers and spandrels in the structural response of regular masonry frames against horizontal loading. A sensitivity analysis is carried out for thirty geometrical configurations of piers and spandrels under two different vertical loading conditions. The numerical analyses are performed with the use of a continuum finite element model enhanced with a crack-tracking technique. This approach is chosen due to its capacity to model accurately cracking phenomena in quasi-brittle materials, yielding realistic collapse mechanisms. The study aims to give an insight on the variation of the capacity and ductility of the structure, as well as the obtained damage pattern, in respect to the relative geometry between piers and spandrels. The results are also useful for the calibration of simplified modelling approaches.