Patients with type 2 diabetes are at increased risk for post-PCI complications including stent thrombosis and restenosis. Stent edge dissections (SEDs) have been associated with these complications. This study assessed incidence and predictors of SEDs in patients with type 2 diabetes using optical coherence tomography (OCT). Intravascular lesion parameters and plaque morphology were investigated pre- and post-PCI using OCT in 73 type 2 diabetic patients with 90 lesions and 166 visible stent edges. We detected 42 (25.3 %) SEDs in 166 stent edges and 37 (41.1 %) SEDs in 90 lesions. More SEDs occurred if the border of the stent had been placed within diseased vessel segments with predominantly fibrous (42.9 %) and fibrocalcific (40.5 %) plaques compared to healthy vessel wall morphology (p < 0.001). Furthermore, the lumen eccentricity of the stent at its edges (SAE) (16.00 ± 6.07 vs. 13.11 ± 5.22 %, p < 0.003) and the stent-edge-to-lumen-area-ratio (1.26 ± 0.27 vs. 0.99 ± 0.20, p < 0.001) were both significantly larger in the presence of SEDs. All of the above parameters were significant predictors for SEDs on uni- and multivariate logistic regression analysis (all p < 0.01), suggesting that the lumen eccentricity of the SAE, the stent-edge-to-lumen-area-ratio and diseased vessel wall morphology of the reference segment adjacent to the stent edge are independent risk factors for the presence of SEDs. These results suggest that diseased vessel wall morphology at the stent edges may promote the occurrence of SEDs and that avoidance of longitudinal and transverse mismatch between stent and vessel could be important to reduce SEDs in cardiovascular high-risk patients with type 2 diabetes.