Background: Failure to achieve optimal stent expansion poses a risk of treatment failure in coronary stenting. Substantial portion of coronary interventions are being performed under only angiographic guidance in Korea. Objective: To evaluate the adequacy of stent expansion of 4 widely-used drug-eluting stents (DES) in angiography-guided coronary intervention. Methods: Total 112 de novo lesions (96 patients) undergoing angiography-guided coronary stenting with Cypher (n=30), Taxus liberte (n=27), Endeavor resolute (n=30), and Xience V (n=25), were quantitatively analyzed using CAAS (Cardiovascular Angiography Analysis System) II v5.7. Minimal lumen diameters were measured at peak pressure during stent deployment (MLD1), after stent deflation (MLD2), and after postdilatation (MLD3). Delivery balloon underexpansion, stent recoil, and stent deficit, were calculated by [predicted delivery balloon diameter – MLD1], [MLD1 – MLD2], and [predicted delivery balloon diameter – MLD2 (or MLD3 in postdilatation)], respectively. Optimal stent deployment was defined as final MLD ��� 90% and ��� 80% of predicted diameter, when reference vessel diameter > 2.5 mm and ��� 2.5 mm, respectively. Results: Lesion and procedural characteristics including reference diameter, MLD, lesion type and length, and stent diameter and length, were similar between 4 stents. For deploying stent balloon, higher than nominal pressure (additional 1-8, median 3 mmHg) were used in 83% (93/112) at the operator���s discretion. Median (25th-75th IQR) delivery balloon underexpansion, stent recoil, and stent deficit, were 0.42 mm (0.29-0.53), 0.11 mm (0.00-0.32), and 0.58 mm (0.34-0.88), representing 13% (9-17), 5% (0-13), and 18% (11-26) less than predicted diameter, respectively. After stent deflation, optimal deployment was observed in 28% (31/112). Postdilatation was performed in 46% (37/81) of lesions with suboptimal expansion, which increased the optimal deployment rate by 73% (27/37). After postdilatation, final optimal stent deployment was achieved in 52% (58/112). There were no significant differences in the magnitude of stent underexpansion, recoil, and the optimal stent deployment rate between 4 stents. Conclusion: Suboptimal stent expansion due to delivery balloon underexpansion and stent recoil is common in angiography-guided coronary stenting, even with the higher deployment pressure. Four different DESs yield similar suboptimal stent expansion. High pressure postdilatation and guidance of intravascular ultrasound may improve adequacy of stent expansion.