Background: Coronary artery spasm, an intense vasoconstriction of coronary arteries that causes total or sub-total vessel occlusion presenting as acute coronary syndrome (ACS), “which can be an ST segment elevation myocardial infarction (STEMI), non-ST elevation myocardial infarction (NSTEMI), or unstable angina (UA). Case Report: We are presenting two different patterns of coronary artery spasm: one focal and one diffuse. The first presenting as STEMI and the second as NSTEMI to raise the possibility of routine intra-coronary injection of nitroglycerine to uncovering coronary spasm in acute coronary syndrome (ASC) and preventing inappropriate stenting, influencing the clinical outcomes associated with inappropriate stenting in the setting of coronary artery spasm. Conclusion: Although the use of intra-coronary nitroglycerin is very frequent during percutaneous intervention (PCI) in vessels sizing, it should be routinely used in acute coronary syndrome (ACS) patient prior to stenting and thus preventing inappropriate stenting, influencing the clinical outcomes associated with inappropriate stenting in the setting of coronary artery spasm.