Small vessel diameter and residual platelet reactivity are independent predictors of thrombotic events after percutaneous coronary intervention (PCI). We sought to determine whether an interaction exists between residual platelet reactivity and stent diameter regarding the occurrence of stent thrombosis and other adverse events after PCI. We stratified patients in the prospective ADAPT-DES registry who underwent single-lesion PCI according to if they received a small diameter stent (SDS, defined as a stent with a diameter of 2.25 mm). Patients receiving an SDS were compared with patients receiving a stent ≥2.5 mm using Kaplan-Meier rates and multivariable Cox proportional hazards regression. We defined major adverse cardiac events (MACE) as the composite of cardiac death, myocardial infarction, and stent thrombosis (ST). Among 5,608 patients who underwent single-lesion PCI in ADAPT-DES, 222 (4.0%) patients received an SDS. Patients with an SDS were more likely than patients without an SDS to have 3-vessel disease but received, on average, fewer stents and were less likely to present with a thrombotic lesion. Receiving versus not receiving an SDS was associated with increased risk of ST (adjusted hazard ratio 4.35, 95% confidence interval 1.95 to 9.73, p <0.001) as well as MACE (adjusted hazard ratio 1.75, 95% confidence interval 1.11 to 2.75, p = 0.02). There was no statistical interaction between platelet reactivity and SDS regarding ST (p = 0.12) or MACE (p = 0.51). In conclusion, PCI with small drug-eluting stents is associated with a high risk of thrombotic events, including ST. Further studies should explore whether alternative treatment strategies are appropriate in small vessels.