Guide catheter extension system (GCES) is a valuable tool for interventional cardiologists, especially in complex cases. GCES increases guide back-up support and is crucial in complex PCI procedures, particularly in cases of severe calcification and tortuosity. Apart from their primary use to increase back-up support of guide by providing coaxial alignment, deep intubation and facilitation of stent delivery, GCES are now being increasingly used in different clinical indications including complex and high-risk coronary intervention interventions.