One of the primary goals in tall building design is the optimum design of service core where the vertical transportation, building services, HVAC elements etc. are situated. Particularly for supertall (+300) office buildings, a significant portion of the core space is occupied by elevators when compared to the rest of the service core elements. Actually, with the utilization of recently developed elevator technologies, it is possible to decrease the elevator footprint area and thereby to decrease the service core area. Nevertheless, the core of a tall building usually is also a part of the lateral load resisting system, namely as a structural core. This study aims to investigate the effects of service core reduction which is a consequence of the elevator footprint decrease on interior and exterior tall building structures. Generic computer models of outriggered frame and framed-tube buildings with 300m height (75 story) are produced. Then, the service core area of both buildings is decreased considering the effects of recent advances in elevator technology. First, the strength and the stiffness constraints as well as serviceability of primary and reduced core buildings are evaluated in terms of code-based design loads for each outriggered frame and framed-tube structural systems. Then, primary and reduced core buildings of outriggered frame and framed-tube structural systems are compared in terms of the change in top drift to building height ratio, the increase in leasable area and to access to natural light.