In clinical practice, adequate stent deployment has an important effect on immediate and long-term results after percutaneous coronary interventions. In particular, suboptimal or incomplete stent expansion is associated with increased restenosis and target vessel revascularization rates and, especially with drug-eluting stents (DES), might also predispose to stent thrombosis. Notwithstanding the significant improvement in technique and materials in the last decade, adjunctive high-pressure balloon dilation is still necessary to improve the minimum stent area and the uniform volumetric stent expansion in a majority of the cases. Indeed, in the published reports, the incidence of incomplete stent deployment ranges from 20% to 30% of cases, but it is significantly higher in trials in which stent expansion was assessed by intravascular ultrasound. Although there are not enough randomized studies about this topic, data from published reports continue to support the use of proper post-dilation in the majority of patients undergoing both bare-metal stent and DES implantation. This review will summarize the different anatomical, clinical, and device-related variables for increased risk of suboptimal stent delivery, highlighting the importance of adequate high-pressure post-dilation to obtain optimal stent expansion to positively affect stent thrombosis and restenosis.