The document presents a comparative study of seismic analysis of regular and irregular structures with and without post-tensioned slabs. A 10-story building model is created in ETABS software and response spectrum analysis is performed. Results show displacement is higher in regular structures compared to similar structures using post-tensioned slabs. Irregular structures are more affected by torsion during seismic activity. The aim is to analyze and compare seismic responses of structures with and without post-tensioned slabs to study their performance.